From 11e21fc5e064813cb5d97c9d029c0b4e01f59a73 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 11:06:56 -0500 Subject: [PATCH 01/47] michaelmoss java-collections --- src/main/java/Collections/Practice/CollectionBasics.java | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/main/java/Collections/Practice/CollectionBasics.java b/src/main/java/Collections/Practice/CollectionBasics.java index e45cb49..f434778 100644 --- a/src/main/java/Collections/Practice/CollectionBasics.java +++ b/src/main/java/Collections/Practice/CollectionBasics.java @@ -33,6 +33,9 @@ public static int sum(Collection numbers) { // TODO: // Loop through the collection // Add each number to total + for (Integer num : numbers) { + total += num; + } return total; } From e755c7e3a55a3cb581a8dcbe5f5dbb97c985d465 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 11:33:57 -0500 Subject: [PATCH 02/47] michaelmoss java-collections --- src/main/java/Collections/Practice/CollectionBasics.java | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/src/main/java/Collections/Practice/CollectionBasics.java b/src/main/java/Collections/Practice/CollectionBasics.java index f434778..f9f48ca 100644 --- a/src/main/java/Collections/Practice/CollectionBasics.java +++ b/src/main/java/Collections/Practice/CollectionBasics.java @@ -51,7 +51,12 @@ public static int countEven(Collection numbers) { // TODO: // Loop through the collection + for (Integer num : numbers) { // If the number is even, increase count + if (num % 2 == 0) { + count++; + } + } return count; } From c022c66ad372935ad6054426c44c5763f303bdfa Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 11:43:49 -0500 Subject: [PATCH 03/47] michaelmoss java-collections --- src/main/java/Collections/Practice/CollectionBasics.java | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/main/java/Collections/Practice/CollectionBasics.java b/src/main/java/Collections/Practice/CollectionBasics.java index f9f48ca..b2f32f1 100644 --- a/src/main/java/Collections/Practice/CollectionBasics.java +++ b/src/main/java/Collections/Practice/CollectionBasics.java @@ -72,7 +72,13 @@ public static int findMax(Collection numbers) { // TODO: // Loop through numbers + for (Integer num : numbers) { // Update max if current number is larger + if (num > max) { + max = num; + } + } + return max; } From 9b71446e7e9269dc8b65b5f6b54cebd6e89c3620 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 17:50:29 -0500 Subject: [PATCH 04/47] michaelmoss java-collections --- .../Practice/CollectionBasics.java | 21 +++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/src/main/java/Collections/Practice/CollectionBasics.java b/src/main/java/Collections/Practice/CollectionBasics.java index b2f32f1..b7c0e24 100644 --- a/src/main/java/Collections/Practice/CollectionBasics.java +++ b/src/main/java/Collections/Practice/CollectionBasics.java @@ -91,10 +91,15 @@ public static int findMax(Collection numbers) { */ public static boolean hasDuplicates(Collection numbers) { + + + // TODO: // Hint: // Compare the size of a collection with the size of a Set + + return false; } @@ -110,6 +115,11 @@ public static int countOccurrences(Collection numbers, int target) { // TODO: // Loop through numbers // If number equals target, increase count + for (Integer num : numbers) { + if (num == target) { + count++; + } + } return count; } @@ -126,8 +136,15 @@ public static Collection filterGreaterThanTwenty(Collection nu // TODO: // Loop through numbers - // Add numbers greater than 20 to result + for (Integer num : numbers) { + // Add numbers greater than 20 to result + if (num > 20) { + result.add(num); + + } + } + return result; } -} + } From 097198a85cb91fa331ccd622cab06fff0250fb9a Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 18:56:51 -0500 Subject: [PATCH 05/47] michaelmoss java-collections --- .../CollectionsHackerrankProblems.java | 23 ++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java b/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java index 6c2f4e1..a6c70a5 100644 --- a/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java +++ b/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java @@ -1,15 +1,26 @@ package CollectionsHackerrank; +import java.util.Arrays; import java.util.List; import java.util.Map; import java.util.Queue; +import java.util.Set; +import java.util.ArrayList; +import java.util.LinkedHashSet; +import java.util.Scanner; + public class CollectionsHackerrankProblems { - public class CollectionsHackerrankPractice { + public static class CollectionsHackerrankPractice { public static void main(String[] args) { // You can test your methods here + List numbers = Arrays.asList(1,2,2,3,4,4,5); + System.out.println(removeDuplicates(numbers)); + } + + } @@ -24,8 +35,14 @@ public static void main(String[] args) { public static List removeDuplicates(List numbers) { // TODO: Implement this method + Set uniqueNumbers = new LinkedHashSet<>(numbers); // removes duplicates + List result = new ArrayList<>(uniqueNumbers); + + + + + return result; - return null; } /* @@ -175,4 +192,4 @@ public static int maxSlidingWindowSum(List numbers, int k) { return 0; } } -} + From a94778cd87c7b1bd875792fd8b682125fa43c798 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 19:21:06 -0500 Subject: [PATCH 06/47] michaelmoss java-collections --- .../CollectionsHackerrankProblems.java | 28 +++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java b/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java index a6c70a5..ab2c4f3 100644 --- a/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java +++ b/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java @@ -7,7 +7,7 @@ import java.util.Set; import java.util.ArrayList; import java.util.LinkedHashSet; -import java.util.Scanner; +import java.util.HashMap; public class CollectionsHackerrankProblems { @@ -56,10 +56,22 @@ public static List removeDuplicates(List numbers) { public static Map countFrequency(List numbers) { // TODO: Implement this method + Map frequencyMap = new HashMap<>(); - return null; + for (Integer num : numbers) { + if (frequencyMap.containsKey(num)) { + frequencyMap.put(num, frequencyMap.get(num) + 1); + } else { + frequencyMap.put(num, 1); + } + } + + return frequencyMap; } + + + /* Problem 3 Return the first number that appears only once. @@ -71,6 +83,18 @@ public static Map countFrequency(List numbers) { public static Integer firstUnique(List numbers) { // TODO: Implement this method + Map frequencyMap = new HashMap<>(); + + for (Integer num : numbers) { + frequencyMap.put(num, frequencyMap.getOrDefault(num, 0) + 1); + } + + for (Integer num : numbers) { + if (frequencyMap.get(num) == 1) { + return num; + } + } + return null; } From b704baf3c6387a90c4890208e3787fefa1913efb Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 19:59:44 -0500 Subject: [PATCH 07/47] michaelmoss java-collections --- .../CollectionsHackerrankProblems.java | 113 +++++++++++++++++- 1 file changed, 107 insertions(+), 6 deletions(-) diff --git a/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java b/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java index ab2c4f3..7a62729 100644 --- a/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java +++ b/src/main/java/CollectionsHackerrank/CollectionsHackerrankProblems.java @@ -8,6 +8,8 @@ import java.util.ArrayList; import java.util.LinkedHashSet; import java.util.HashMap; +import java.util.HashSet; +import java.util.Stack; public class CollectionsHackerrankProblems { @@ -112,10 +114,23 @@ public static Integer firstUnique(List numbers) { public static boolean twoSum(List numbers, int target) { // TODO: Implement this method + Set seen = new HashSet<>(); + + for (int num : numbers) { + int complement = target - num; + + if (seen.contains(complement)) { + return true; + } + + seen.add(num); + } return false; } + + /* Problem 5 Count how many unique words exist in a list. @@ -127,10 +142,16 @@ public static boolean twoSum(List numbers, int target) { public static int countUniqueWords(List words) { // TODO: Implement this method + Set uniqueWords = new HashSet<>(); - return 0; + for (String word : words) { + uniqueWords.add(word); + } + + return uniqueWords.size(); } + /* Problem 6 Reverse a queue. @@ -142,10 +163,23 @@ public static int countUniqueWords(List words) { public static Queue reverseQueue(Queue queue) { // TODO: Implement this method + Stack stack = new Stack<>(); - return null; + // Move elements from queue to stack + while (!queue.isEmpty()) { + stack.push(queue.poll()); + } + + // Move elements back to queue + while (!stack.isEmpty()) { + queue.add(stack.pop()); + } + + return queue; } + + /* Problem 7 Determine whether parentheses are balanced. @@ -160,10 +194,28 @@ public static Queue reverseQueue(Queue queue) { public static boolean isBalanced(String expression) { // TODO: Implement this method + Stack stack = new Stack<>(); - return false; + for (char c : expression.toCharArray()) { + + if (c == '(') { + stack.push(c); + } + else if (c == ')') { + + if (stack.isEmpty()) { + return false; + } + + stack.pop(); + } + } + + return stack.isEmpty(); } + + /* Problem 8 Return the number that appears most frequently in the list. @@ -175,10 +227,27 @@ public static boolean isBalanced(String expression) { public static Integer mostFrequent(List numbers) { // TODO: Implement this method + Map frequency = new HashMap<>(); - return null; + for (Integer num : numbers) { + frequency.put(num, frequency.getOrDefault(num, 0) + 1); + } + + int maxCount = 0; + Integer result = null; + + for (Map.Entry entry : frequency.entrySet()) { + if (entry.getValue() > maxCount) { + maxCount = entry.getValue(); + result = entry.getKey(); + } + } + + return result; } + + /* Problem 9 Group words based on their length. @@ -195,10 +264,24 @@ public static Integer mostFrequent(List numbers) { public static Map> groupByLength(List words) { // TODO: Implement this method + Map> map = new HashMap<>(); - return null; + for (String word : words) { + + int length = word.length(); + + if (!map.containsKey(length)) { + map.put(length, new ArrayList<>()); + } + + map.get(length).add(word); + } + + return map; } + + /* Problem 10 Return the maximum sum of any window of size k. @@ -212,8 +295,26 @@ public static Map> groupByLength(List words) { public static int maxSlidingWindowSum(List numbers, int k) { // TODO: Implement this method + int windowSum = 0; + + // First window + for (int i = 0; i < k; i++) { + windowSum += numbers.get(i); + } - return 0; + int maxSum = windowSum; + + // Slide the window + for (int i = k; i < numbers.size(); i++) { + windowSum += numbers.get(i); // add next + windowSum -= numbers.get(i - k); // remove previous + maxSum = Math.max(maxSum, windowSum); + } + + return maxSum; } + + + } From fd353f9e69a907bbf5184210c21c421997d671b4 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 20:13:33 -0500 Subject: [PATCH 08/47] michaelmoss java-collections --- src/main/java/Iterable/Examples/IteratorDemo.java | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/src/main/java/Iterable/Examples/IteratorDemo.java b/src/main/java/Iterable/Examples/IteratorDemo.java index b09fca7..6003ccd 100644 --- a/src/main/java/Iterable/Examples/IteratorDemo.java +++ b/src/main/java/Iterable/Examples/IteratorDemo.java @@ -26,6 +26,11 @@ public static void main(String[] args) { // TODO: // Use iterator.hasNext() and iterator.next() // Print each number + while (iterator.hasNext()) { + Integer number = iterator.next(); + System.out.println(number); + } + System.out.println("\nRemoving odd numbers using Iterator"); @@ -35,6 +40,13 @@ public static void main(String[] args) { // TODO: // Use iterator to remove odd numbers // Remember: use iterator.remove() + while (iterator.hasNext()) { + Integer number = iterator.next(); + + if (number % 2 != 0) { + iterator.remove(); + } + } System.out.println("\nUpdated list:"); From 1745ae925d7d453900e053258693214e5de7b6c1 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 20:18:20 -0500 Subject: [PATCH 09/47] michaelmoss java-collections --- .../java/Iterable/Examples/ForEachLoopDemo.java | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/src/main/java/Iterable/Examples/ForEachLoopDemo.java b/src/main/java/Iterable/Examples/ForEachLoopDemo.java index a6d2198..4c79ebd 100644 --- a/src/main/java/Iterable/Examples/ForEachLoopDemo.java +++ b/src/main/java/Iterable/Examples/ForEachLoopDemo.java @@ -17,12 +17,20 @@ public static void main(String[] args) { // TODO: // Use a for-each loop to print each student name + for (String student : students) { + System.out.println(student); + } + System.out.println("\nPrinting students in uppercase:"); // TODO: // Use a for-each loop to print each name in uppercase + for (String student : students) { + System.out.println(student.toUpperCase()); + } + System.out.println("\nCount the number of students:"); @@ -31,6 +39,11 @@ public static void main(String[] args) { // TODO: // Use a for-each loop to count how many students are in the list + for (String student : students) { + System.out.println(student.toUpperCase()); + } + + System.out.println("Total students: " + count); } From b9c59b13f693b80a4771ea1a0560dfba128c4b58 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 20:25:26 -0500 Subject: [PATCH 10/47] michaelmoss java-collections --- src/main/java/Iterable/Practice/IterableWarmups.java | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/main/java/Iterable/Practice/IterableWarmups.java b/src/main/java/Iterable/Practice/IterableWarmups.java index 9e9de94..92385fb 100644 --- a/src/main/java/Iterable/Practice/IterableWarmups.java +++ b/src/main/java/Iterable/Practice/IterableWarmups.java @@ -30,6 +30,9 @@ public static int sum(Iterable numbers) { // TODO: // Use a for-each loop to calculate the sum + for (Integer num : numbers) { + total += num; + } return total; } From 1c1345cff98cd1707ea2eac8ab6a417a6b9f3f4c Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 20:34:59 -0500 Subject: [PATCH 11/47] michaelmoss java-collections --- src/main/java/Iterable/Practice/IterableWarmups.java | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/main/java/Iterable/Practice/IterableWarmups.java b/src/main/java/Iterable/Practice/IterableWarmups.java index 92385fb..c9840d0 100644 --- a/src/main/java/Iterable/Practice/IterableWarmups.java +++ b/src/main/java/Iterable/Practice/IterableWarmups.java @@ -49,11 +49,18 @@ public static int countEven(Iterable numbers) { // TODO: // Loop through numbers // Increment count if number is even + for (Integer num : numbers) { + if (num % 2 == 0) { + count++; + } + } return count; } + + /* PROBLEM 3 Return the maximum value From 76624b1a4aa82b582f4d0e624e45d16ae65cc72d Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 20:38:05 -0500 Subject: [PATCH 12/47] michaelmoss java-collections --- src/main/java/Iterable/Practice/IterableWarmups.java | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/main/java/Iterable/Practice/IterableWarmups.java b/src/main/java/Iterable/Practice/IterableWarmups.java index c9840d0..3de4056 100644 --- a/src/main/java/Iterable/Practice/IterableWarmups.java +++ b/src/main/java/Iterable/Practice/IterableWarmups.java @@ -72,11 +72,18 @@ public static int findMax(Iterable numbers) { // TODO: // Loop through numbers // Update max if current number is larger + for (Integer num : numbers) { + if (num > max) { + max = num; + } + } return max; } + + /* PROBLEM 4 (BONUS) Count how many times a word appears From 1c1921762e9e096bba22bf5d18e429317eb4424b Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 21:19:56 -0500 Subject: [PATCH 13/47] michaelmoss java-collections --- .../java/Iterable/Practice/IterableWarmups.java | 7 +++++++ .../java/Lists/ArrayLists/ArrayListProblems.java | 13 ++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/src/main/java/Iterable/Practice/IterableWarmups.java b/src/main/java/Iterable/Practice/IterableWarmups.java index 3de4056..84cc06a 100644 --- a/src/main/java/Iterable/Practice/IterableWarmups.java +++ b/src/main/java/Iterable/Practice/IterableWarmups.java @@ -95,7 +95,14 @@ public static int countMatches(Iterable words, String target) { // TODO: // Loop through words // Compare each word to target + for (String word : words) { + if (word.equals(target)) { + count++; + } + } return count; } + + } diff --git a/src/main/java/Lists/ArrayLists/ArrayListProblems.java b/src/main/java/Lists/ArrayLists/ArrayListProblems.java index baf4dfa..ebaeb53 100644 --- a/src/main/java/Lists/ArrayLists/ArrayListProblems.java +++ b/src/main/java/Lists/ArrayLists/ArrayListProblems.java @@ -34,10 +34,21 @@ public static void main(String[] args) { public static int sum(List nums) { // TODO: Implement this method + int total = 0; - return 0; + for (int num : nums) { + total += num; + } + + return total; } + + + + + + /* Problem 2 Count how many EVEN numbers exist in the list. From 89db66a62b7a75ca9f89d7ef5b16ac6c92e05bbc Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 21:34:38 -0500 Subject: [PATCH 14/47] michaelmoss java-collections --- .../Lists/ArrayLists/ArrayListProblems.java | 31 +++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/src/main/java/Lists/ArrayLists/ArrayListProblems.java b/src/main/java/Lists/ArrayLists/ArrayListProblems.java index ebaeb53..c79e017 100644 --- a/src/main/java/Lists/ArrayLists/ArrayListProblems.java +++ b/src/main/java/Lists/ArrayLists/ArrayListProblems.java @@ -60,10 +60,19 @@ public static int sum(List nums) { public static int countEvens(List nums) { // TODO: Implement this method + int count = 0; - return 0; + for (int num : nums) { + if (num % 2 == 0) { + count++; + } + } + + return count; } + + /* Problem 3 Determine if the list contains any duplicate values. @@ -78,10 +87,19 @@ public static int countEvens(List nums) { public static boolean hasDuplicate(List nums) { // TODO: Implement this method + for (int i = 0; i < nums.size(); i++) { + for (int j = i + 1; j < nums.size(); j++) { + if (nums.get(i).equals(nums.get(j))) { + return true; + } + } + } return false; } + + /* Problem 4 Return the largest number in the list. @@ -93,10 +111,19 @@ public static boolean hasDuplicate(List nums) { public static int findMax(List nums) { // TODO: Implement this method + int max = nums.get(0); + + for (int num : nums) { + if (num > max) { + max = num; + } + } - return 0; + return max; } + + /* Problem 5 Return a NEW list that contains the elements of the original list in reverse order. From 84e270254f22896d03dec34b39d19e91e0a889c4 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 21:37:42 -0500 Subject: [PATCH 15/47] michaelmoss java-collections --- src/main/java/Lists/ArrayLists/ArrayListProblems.java | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/src/main/java/Lists/ArrayLists/ArrayListProblems.java b/src/main/java/Lists/ArrayLists/ArrayListProblems.java index c79e017..97d5f2d 100644 --- a/src/main/java/Lists/ArrayLists/ArrayListProblems.java +++ b/src/main/java/Lists/ArrayLists/ArrayListProblems.java @@ -138,6 +138,14 @@ public static List reverse(List nums) { // TODO: Implement this method - return null; + List reversed = new ArrayList<>(); + + for (int i = nums.size() - 1; i >= 0; i--) { + reversed.add(nums.get(i)); + } + + return reversed; } + + } From bc7bbd8737903d55a3015b96bdd18e7b54a7e1d3 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 21:50:00 -0500 Subject: [PATCH 16/47] michaelmoss java-collections --- src/main/java/Lists/LinkedLists/LinkedListProblems.java | 2 ++ 1 file changed, 2 insertions(+) diff --git a/src/main/java/Lists/LinkedLists/LinkedListProblems.java b/src/main/java/Lists/LinkedLists/LinkedListProblems.java index 178a2ba..ce66b1c 100644 --- a/src/main/java/Lists/LinkedLists/LinkedListProblems.java +++ b/src/main/java/Lists/LinkedLists/LinkedListProblems.java @@ -38,6 +38,8 @@ public static void main(String[] args) { public static void addToFront(LinkedList list, int value) { // TODO: Implement this method + list.addFirst(value); + } From 6c5806a58f0717b4c2b70ed19c1737c44cb847ee Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 21:59:03 -0500 Subject: [PATCH 17/47] michaelmoss java-collections --- src/main/java/Lists/LinkedLists/LinkedListProblems.java | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/main/java/Lists/LinkedLists/LinkedListProblems.java b/src/main/java/Lists/LinkedLists/LinkedListProblems.java index ce66b1c..ee18ab6 100644 --- a/src/main/java/Lists/LinkedLists/LinkedListProblems.java +++ b/src/main/java/Lists/LinkedLists/LinkedListProblems.java @@ -54,6 +54,7 @@ public static void addToFront(LinkedList list, int value) { public static void addToEnd(LinkedList list, int value) { // TODO: Implement this method + list.addLast(value); } @@ -68,7 +69,7 @@ public static void addToEnd(LinkedList list, int value) { public static void removeFirstElement(LinkedList list) { // TODO: Implement this method - + list.removeFirst(); } /* From 596f9728e8b36d1eecc80f1b27d68edb96814878 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:06:03 -0500 Subject: [PATCH 18/47] michaelmoss java-collections --- .../java/Lists/LinkedLists/LinkedListProblems.java | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/src/main/java/Lists/LinkedLists/LinkedListProblems.java b/src/main/java/Lists/LinkedLists/LinkedListProblems.java index ee18ab6..885edaf 100644 --- a/src/main/java/Lists/LinkedLists/LinkedListProblems.java +++ b/src/main/java/Lists/LinkedLists/LinkedListProblems.java @@ -83,7 +83,7 @@ public static void removeFirstElement(LinkedList list) { public static void removeLastElement(LinkedList list) { // TODO: Implement this method - + list.removeLast(); } /* @@ -97,6 +97,9 @@ public static void removeLastElement(LinkedList list) { public static int getFirstElement(LinkedList list) { // TODO: Implement this method + if (!list.isEmpty()) { + list.removeLast(); + } return 0; } @@ -112,7 +115,9 @@ public static int getFirstElement(LinkedList list) { public static int getLastElement(LinkedList list) { // TODO: Implement this method - - return 0; + return list.getLast(); } + + + } From edbaa2371e6d27085dbe460bad9b54bcf0905218 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:18:32 -0500 Subject: [PATCH 19/47] michaelmoss java-collections --- src/main/java/Maps/HashMap/HashMapProblems.java | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/src/main/java/Maps/HashMap/HashMapProblems.java b/src/main/java/Maps/HashMap/HashMapProblems.java index 04b5567..6cce3a1 100644 --- a/src/main/java/Maps/HashMap/HashMapProblems.java +++ b/src/main/java/Maps/HashMap/HashMapProblems.java @@ -35,9 +35,11 @@ public static void main(String[] args) { public static void addItem(Map map, String item, int quantity) { // TODO: Implement this method - + map.put(item, quantity); } + + /* Problem 2 Return the quantity of a specific item. @@ -49,10 +51,11 @@ public static void addItem(Map map, String item, int quantity) public static int getQuantity(Map map, String item) { // TODO: Implement this method - - return 0; + return map.get(item); } + + /* Problem 3 Update the quantity of an existing item. @@ -64,9 +67,11 @@ public static int getQuantity(Map map, String item) { public static void updateQuantity(Map map, String item, int newQuantity) { // TODO: Implement this method - + map.put(item, newQuantity); } + + /* Problem 4 Remove an item from the map. From 29f76fdd604503c2bada37ea44772aab10a1b4ad Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:35:28 -0500 Subject: [PATCH 20/47] michaelmoss java-collections --- src/main/java/Maps/HashMap/HashMapProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Maps/HashMap/HashMapProblems.java b/src/main/java/Maps/HashMap/HashMapProblems.java index 6cce3a1..ddfab0c 100644 --- a/src/main/java/Maps/HashMap/HashMapProblems.java +++ b/src/main/java/Maps/HashMap/HashMapProblems.java @@ -83,9 +83,11 @@ public static void updateQuantity(Map map, String item, int new public static void removeItem(Map map, String item) { // TODO: Implement this method - + map.remove(item); } + + /* Problem 5 Count how many times each number appears in a list. From 70a3166b9cb44259b981966db09406ec18f8fded Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:36:58 -0500 Subject: [PATCH 21/47] michaelmoss java-collections --- src/main/java/Maps/HashMap/HashMapProblems.java | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/src/main/java/Maps/HashMap/HashMapProblems.java b/src/main/java/Maps/HashMap/HashMapProblems.java index ddfab0c..9f7f26d 100644 --- a/src/main/java/Maps/HashMap/HashMapProblems.java +++ b/src/main/java/Maps/HashMap/HashMapProblems.java @@ -99,7 +99,18 @@ public static void removeItem(Map map, String item) { public static Map countFrequency(List numbers) { // TODO: Implement this method + Map frequencyMap = new HashMap<>(); - return null; + for (Integer num : numbers) { + if (frequencyMap.containsKey(num)) { + frequencyMap.put(num, frequencyMap.get(num) + 1); + } else { + frequencyMap.put(num, 1); + } + } + + return frequencyMap; } + + } From 0ea595e4c471cc4f3f749c42f5c10c153519b18b Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:46:50 -0500 Subject: [PATCH 22/47] michaelmoss java-collections --- .../java/Maps/LinkedHashMap/LinkedHashMapProblems.java | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java index e8bbdc2..60fbb86 100644 --- a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java +++ b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java @@ -33,9 +33,11 @@ public static void main(String[] args) { public static void addStudent(Map map, String name, int grade) { // TODO: Implement this method - + map.put(name, grade); } + + /* Problem 2 Update the grade of an existing student. @@ -47,9 +49,11 @@ public static void addStudent(Map map, String name, int grade) public static void updateGrade(Map map, String name, int newGrade) { // TODO: Implement this method - + map.put(name, newGrade); } + + /* Problem 3 Remove a student from the LinkedHashMap. From d2e3e7959fdc92735c777a8e6b5187b8ba64102a Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:50:19 -0500 Subject: [PATCH 23/47] michaelmoss java-collections --- src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java index 60fbb86..24b820e 100644 --- a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java +++ b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java @@ -65,9 +65,11 @@ public static void updateGrade(Map map, String name, int newGra public static void removeStudent(Map map, String name) { // TODO: Implement this method - + map.remove(name); } + + /* Problem 4 Return the first student inserted into the LinkedHashMap. From ac90e78a04ce8770c1b9c2bc745313d89c9b8a08 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:52:36 -0500 Subject: [PATCH 24/47] michaelmoss java-collections --- src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java index 24b820e..ea262ca 100644 --- a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java +++ b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java @@ -81,10 +81,11 @@ public static void removeStudent(Map map, String name) { public static String getFirstInserted(Map map) { // TODO: Implement this method - - return null; + return map.keySet().iterator().next(); } + + /* Problem 5 Given a list of words, return a LinkedHashMap that counts From 9edf4fb37b022e15e10c3eb25d1b6e0a8ad3443f Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Fri, 6 Mar 2026 23:55:24 -0500 Subject: [PATCH 25/47] michaelmoss java-collections --- .../java/Maps/LinkedHashMap/LinkedHashMapProblems.java | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java index ea262ca..de87a7c 100644 --- a/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java +++ b/src/main/java/Maps/LinkedHashMap/LinkedHashMapProblems.java @@ -98,7 +98,14 @@ public static String getFirstInserted(Map map) { public static Map wordFrequency(List words) { // TODO: Implement this method + Map map = new LinkedHashMap<>(); - return null; + for (String word : words) { + map.put(word, map.getOrDefault(word, 0) + 1); + } + + return map; } + + } From b1af621202b74a6ae757d28b1aba37c858c2052a Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:14:16 -0500 Subject: [PATCH 26/47] michaelmoss java-collections --- src/main/java/Maps/TreeMap/TreeMapProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Maps/TreeMap/TreeMapProblems.java b/src/main/java/Maps/TreeMap/TreeMapProblems.java index b101d2e..bddbe56 100644 --- a/src/main/java/Maps/TreeMap/TreeMapProblems.java +++ b/src/main/java/Maps/TreeMap/TreeMapProblems.java @@ -31,9 +31,11 @@ public static void main(String[] args) { public static void addPlayer(TreeMap map, int rank, String name) { // TODO: Implement this method - + map.put(rank, name); } + + /* Problem 2 Return the player with the highest ranking (smallest key). From 3f0e0001f2810fd3454d55e9b0c3d092690acb2e Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:25:43 -0500 Subject: [PATCH 27/47] michaelmoss java-collections --- src/main/java/Maps/TreeMap/TreeMapProblems.java | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/main/java/Maps/TreeMap/TreeMapProblems.java b/src/main/java/Maps/TreeMap/TreeMapProblems.java index bddbe56..1f5a2fd 100644 --- a/src/main/java/Maps/TreeMap/TreeMapProblems.java +++ b/src/main/java/Maps/TreeMap/TreeMapProblems.java @@ -47,10 +47,11 @@ Return the player with the highest ranking (smallest key). public static String getTopPlayer(TreeMap map) { // TODO: Implement this method - - return null; + return map.get(map.firstKey()); } + + /* Problem 3 Return the player with the lowest ranking (largest key). From 9e14e61476ea7b9258634edf82be4d2fa099d61f Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:27:20 -0500 Subject: [PATCH 28/47] michaelmoss java-collections --- src/main/java/Maps/TreeMap/TreeMapProblems.java | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/main/java/Maps/TreeMap/TreeMapProblems.java b/src/main/java/Maps/TreeMap/TreeMapProblems.java index 1f5a2fd..716290e 100644 --- a/src/main/java/Maps/TreeMap/TreeMapProblems.java +++ b/src/main/java/Maps/TreeMap/TreeMapProblems.java @@ -63,10 +63,10 @@ Return the player with the lowest ranking (largest key). public static String getLowestPlayer(TreeMap map) { // TODO: Implement this method - - return null; + return map.get(map.lastKey()); } + /* Problem 4 Remove a player based on their rank. From ee64f154bd229932013ea57d91e3ae99eb023752 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:28:50 -0500 Subject: [PATCH 29/47] michaelmoss java-collections --- src/main/java/Maps/TreeMap/TreeMapProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Maps/TreeMap/TreeMapProblems.java b/src/main/java/Maps/TreeMap/TreeMapProblems.java index 716290e..b2ee070 100644 --- a/src/main/java/Maps/TreeMap/TreeMapProblems.java +++ b/src/main/java/Maps/TreeMap/TreeMapProblems.java @@ -78,9 +78,11 @@ public static String getLowestPlayer(TreeMap map) { public static void removePlayer(TreeMap map, int rank) { // TODO: Implement this method - + map.remove(rank); } + + /* Problem 5 Return the next higher rank after the given rank. From a638e7ea7f550527a17633e4faee60460e38d346 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:29:39 -0500 Subject: [PATCH 30/47] michaelmoss java-collections --- src/main/java/Maps/TreeMap/TreeMapProblems.java | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/main/java/Maps/TreeMap/TreeMapProblems.java b/src/main/java/Maps/TreeMap/TreeMapProblems.java index b2ee070..beb28ce 100644 --- a/src/main/java/Maps/TreeMap/TreeMapProblems.java +++ b/src/main/java/Maps/TreeMap/TreeMapProblems.java @@ -94,7 +94,8 @@ public static void removePlayer(TreeMap map, int rank) { public static Integer getNextRank(TreeMap map, int rank) { // TODO: Implement this method - - return null; + return map.higherKey(rank); } + + } From 8019f7137e89e0505f8b4dbec233cd985d2a7e60 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:34:12 -0500 Subject: [PATCH 31/47] michaelmoss java-collections --- src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java index dac03cf..464fc3f 100644 --- a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java +++ b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java @@ -31,9 +31,11 @@ public static void main(String[] args) { public static void addToFront(ArrayDeque deque, int value) { // TODO: Implement this method - + deque.addFirst(value); } + + /* Problem 2 Add a number to the BACK of the deque. From 610ba664f8f1cd9e5fa645d851d45afbdece3bc8 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:36:01 -0500 Subject: [PATCH 32/47] michaelmoss java-collections --- src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java index 464fc3f..0c1b9f8 100644 --- a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java +++ b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java @@ -47,9 +47,11 @@ public static void addToFront(ArrayDeque deque, int value) { public static void addToBack(ArrayDeque deque, int value) { // TODO: Implement this method - + deque.addLast(value); } + + /* Problem 3 Remove the element at the FRONT of the deque. From 3b1c737c9d2bea9997b0a6203f07fcdaa9d55c53 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:37:15 -0500 Subject: [PATCH 33/47] michaelmoss java-collections --- src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java index 0c1b9f8..f33e017 100644 --- a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java +++ b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java @@ -63,9 +63,11 @@ public static void addToBack(ArrayDeque deque, int value) { public static void removeFront(ArrayDeque deque) { // TODO: Implement this method - + deque.removeFirst(); } + + /* Problem 4 Remove the element at the BACK of the deque. From 4d13f832e6303b90f4aed14df0446bece43fda82 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:39:16 -0500 Subject: [PATCH 34/47] michaelmoss java-collections --- src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java index f33e017..44dbb2d 100644 --- a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java +++ b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java @@ -79,9 +79,11 @@ public static void removeFront(ArrayDeque deque) { public static void removeBack(ArrayDeque deque) { // TODO: Implement this method - + deque.removeLast(); } + + /* Problem 5 Return the FIRST element in the deque without removing it. From a5c362e4303e60bb5beab12dfa590b5f3d1ae2a4 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:42:23 -0500 Subject: [PATCH 35/47] michaelmoss java-collections --- src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java index 44dbb2d..d187c36 100644 --- a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java +++ b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java @@ -95,10 +95,11 @@ public static void removeBack(ArrayDeque deque) { public static Integer peekFront(ArrayDeque deque) { // TODO: Implement this method - - return null; + return deque.peekFirst(); } + + /* Problem 6 Return the LAST element in the deque without removing it. From b33540111021d4778a68145de2e6de2ce463751d Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:44:19 -0500 Subject: [PATCH 36/47] michaelmoss java-collections --- src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java index d187c36..7daa68c 100644 --- a/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java +++ b/src/main/java/Queues/ArrayDeque/ArrayDequeProblems.java @@ -111,7 +111,8 @@ public static Integer peekFront(ArrayDeque deque) { public static Integer peekBack(ArrayDeque deque) { // TODO: Implement this method - - return null; + return deque.peekLast(); } + + } From e1df3c93028ffc3039b6889a2f020ca1e6e1ede0 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 10:54:58 -0500 Subject: [PATCH 37/47] java-collections --- src/main/java/Queues/Deque/DequeProblems.java | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/Deque/DequeProblems.java b/src/main/java/Queues/Deque/DequeProblems.java index 7ef0c06..bc4b2d5 100644 --- a/src/main/java/Queues/Deque/DequeProblems.java +++ b/src/main/java/Queues/Deque/DequeProblems.java @@ -1,14 +1,23 @@ package Queues.Deque; import java.util.Deque; +import java.util.ArrayDeque; + public class DequeProblems { public static void main(String[] args) { // You can test your methods here + Deque deque = new ArrayDeque<>(); + + addFront(deque, 5); + addBack(deque, 10); + + System.out.println(deque); } + /* Problem 1 Add a value to the FRONT of the deque. @@ -20,9 +29,11 @@ public static void main(String[] args) { public static void addFront(Deque deque, int value) { // TODO: Implement this method + deque.addFirst(value); } + /* Problem 2 Add a value to the BACK of the deque. @@ -34,9 +45,11 @@ public static void addFront(Deque deque, int value) { public static void addBack(Deque deque, int value) { // TODO: Implement this method + deque.addLast(value); } + /* Problem 3 Remove and return the FRONT element of the deque. @@ -96,5 +109,5 @@ public static Integer peekBack(Deque deque) { return null; } - } + From 5efc46f7a0cc683f740b7b9d71f2c8306a11ce00 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:01:47 -0500 Subject: [PATCH 38/47] michaelmoss java-collections --- src/main/java/Queues/Deque/DequeProblems.java | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/Deque/DequeProblems.java b/src/main/java/Queues/Deque/DequeProblems.java index bc4b2d5..4e5f598 100644 --- a/src/main/java/Queues/Deque/DequeProblems.java +++ b/src/main/java/Queues/Deque/DequeProblems.java @@ -61,10 +61,13 @@ public static void addBack(Deque deque, int value) { public static Integer removeFront(Deque deque) { // TODO: Implement this method + deque.removeFirst(); + return deque.removeFirst(); - return null; } + + /* Problem 4 Remove and return the BACK element of the deque. From 3873c06074865911456ed5569b9928e07ab4b28e Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:03:15 -0500 Subject: [PATCH 39/47] michaelmoss java-loops --- src/main/java/Queues/Deque/DequeProblems.java | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/Deque/DequeProblems.java b/src/main/java/Queues/Deque/DequeProblems.java index 4e5f598..98db600 100644 --- a/src/main/java/Queues/Deque/DequeProblems.java +++ b/src/main/java/Queues/Deque/DequeProblems.java @@ -79,10 +79,13 @@ public static Integer removeFront(Deque deque) { public static Integer removeBack(Deque deque) { // TODO: Implement this method + deque.removeLast(); + return deque.removeLast(); - return null; } + + /* Problem 5 Return the FRONT element without removing it. From af745cade92ca3d1a1575006ef319d9f841ed094 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:05:02 -0500 Subject: [PATCH 40/47] michaelmoss java-collections --- src/main/java/Queues/Deque/DequeProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/Deque/DequeProblems.java b/src/main/java/Queues/Deque/DequeProblems.java index 98db600..ade3a13 100644 --- a/src/main/java/Queues/Deque/DequeProblems.java +++ b/src/main/java/Queues/Deque/DequeProblems.java @@ -97,10 +97,12 @@ public static Integer removeBack(Deque deque) { public static Integer peekFront(Deque deque) { // TODO: Implement this method + return deque.peekFirst(); - return null; } + + /* Problem 6 Return the BACK element without removing it. From 8cc8a103bc36882fc7cb9204801ad6af636f6b5f Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:05:57 -0500 Subject: [PATCH 41/47] michaelmoss java-collections --- src/main/java/Queues/Deque/DequeProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Queues/Deque/DequeProblems.java b/src/main/java/Queues/Deque/DequeProblems.java index ade3a13..bff87a3 100644 --- a/src/main/java/Queues/Deque/DequeProblems.java +++ b/src/main/java/Queues/Deque/DequeProblems.java @@ -114,8 +114,10 @@ public static Integer peekFront(Deque deque) { public static Integer peekBack(Deque deque) { // TODO: Implement this method + return deque.peekLast(); - return null; } + + } From 9e34580fc798396c5f4e7b612bb2914ebb6f132f Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:15:52 -0500 Subject: [PATCH 42/47] michaelmoss java-collections --- src/main/java/Sets/HashSet/HashSetProblems.java | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/src/main/java/Sets/HashSet/HashSetProblems.java b/src/main/java/Sets/HashSet/HashSetProblems.java index a36c570..f377a4d 100644 --- a/src/main/java/Sets/HashSet/HashSetProblems.java +++ b/src/main/java/Sets/HashSet/HashSetProblems.java @@ -2,14 +2,22 @@ import java.util.List; import java.util.Set; +import java.util.HashSet; public class HashSetProblems { public static void main(String[] args) { // You can test your methods here + Set set = new HashSet<>(); + + addElement(set, "apple"); + + System.out.println(set); // Output: [apple] } + + /* Problem 1 Add an element to the set. @@ -21,9 +29,11 @@ public static void main(String[] args) { public static void addElement(Set set, String value) { // TODO: Implement this method - + set.add(value); } + + /* Problem 2 Check if the set contains a value. From d35e51d0183d7b5691c75fdde7ec1a87898372f9 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:19:37 -0500 Subject: [PATCH 43/47] michaelmoss java-collections --- src/main/java/Sets/HashSet/HashSetProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Sets/HashSet/HashSetProblems.java b/src/main/java/Sets/HashSet/HashSetProblems.java index f377a4d..14f8231 100644 --- a/src/main/java/Sets/HashSet/HashSetProblems.java +++ b/src/main/java/Sets/HashSet/HashSetProblems.java @@ -45,10 +45,12 @@ public static void addElement(Set set, String value) { public static boolean containsValue(Set set, String value) { // TODO: Implement this method + return set.contains(value); - return false; } + + /* Problem 3 Remove a value from the set. From 437977701dc68382ea2da098d1941afd5e232c17 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:20:30 -0500 Subject: [PATCH 44/47] michaelmoss java-collections --- src/main/java/Sets/HashSet/HashSetProblems.java | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/main/java/Sets/HashSet/HashSetProblems.java b/src/main/java/Sets/HashSet/HashSetProblems.java index 14f8231..a623aa9 100644 --- a/src/main/java/Sets/HashSet/HashSetProblems.java +++ b/src/main/java/Sets/HashSet/HashSetProblems.java @@ -62,9 +62,12 @@ public static boolean containsValue(Set set, String value) { public static void removeValue(Set set, String value) { // TODO: Implement this method + set.remove(value); } + + /* Problem 4 Return the number of unique elements in the set. From fba3ef6a9950286be245045c7066690733e1b42a Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:22:09 -0500 Subject: [PATCH 45/47] michaelmoss java-collections --- src/main/java/Sets/HashSet/HashSetProblems.java | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/main/java/Sets/HashSet/HashSetProblems.java b/src/main/java/Sets/HashSet/HashSetProblems.java index a623aa9..c70f224 100644 --- a/src/main/java/Sets/HashSet/HashSetProblems.java +++ b/src/main/java/Sets/HashSet/HashSetProblems.java @@ -79,10 +79,12 @@ public static void removeValue(Set set, String value) { public static int getUniqueCount(Set set) { // TODO: Implement this method + return set.size(); - return 0; } + + /* Problem 5 Given a list of integers, return a HashSet containing only the unique values. From 2ebb2c2baa138ca71ccfb41874feb5e793714a6a Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:23:19 -0500 Subject: [PATCH 46/47] michaelmoss java-collections --- src/main/java/Sets/HashSet/HashSetProblems.java | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/main/java/Sets/HashSet/HashSetProblems.java b/src/main/java/Sets/HashSet/HashSetProblems.java index c70f224..5dd6165 100644 --- a/src/main/java/Sets/HashSet/HashSetProblems.java +++ b/src/main/java/Sets/HashSet/HashSetProblems.java @@ -96,7 +96,8 @@ public static int getUniqueCount(Set set) { public static Set getUniqueValues(List numbers) { // TODO: Implement this method - - return null; + return new HashSet<>(numbers); } + + } From 6d88db90d404ece0e9063730a7dfcc6c685b8439 Mon Sep 17 00:00:00 2001 From: michaelmoss Date: Sat, 7 Mar 2026 11:25:58 -0500 Subject: [PATCH 47/47] michaelmoss java-collections --- src/main/java/Sets/HashSet/HashSetProblems.java | 1 + 1 file changed, 1 insertion(+) diff --git a/src/main/java/Sets/HashSet/HashSetProblems.java b/src/main/java/Sets/HashSet/HashSetProblems.java index 5dd6165..6fad1ce 100644 --- a/src/main/java/Sets/HashSet/HashSetProblems.java +++ b/src/main/java/Sets/HashSet/HashSetProblems.java @@ -100,4 +100,5 @@ public static Set getUniqueValues(List numbers) { } + }