diff --git a/Exercise_1.java b/BInarySearch.java
similarity index 61%
rename from Exercise_1.java
rename to BInarySearch.java
index c3ff1141..e3ecdb26 100644
--- a/Exercise_1.java
+++ b/BInarySearch.java
@@ -1,21 +1,35 @@
-class BinarySearch { 
-    // Returns index of x if it is present in arr[l.. r], else return -1 
-    int binarySearch(int arr[], int l, int r, int x) 
-    { 
-        //Write your code here
-    } 
-  
-    // Driver method to test above 
-    public static void main(String args[]) 
-    { 
-        BinarySearch ob = new BinarySearch(); 
-        int arr[] = { 2, 3, 4, 10, 40 }; 
-        int n = arr.length; 
-        int x = 10; 
-        int result = ob.binarySearch(arr, 0, n - 1, x); 
-        if (result == -1) 
-            System.out.println("Element not present"); 
-        else
-            System.out.println("Element found at index " + result); 
-    } 
-} 
+//Time Complexity : O(log n)
+//Space Complexity : O(1)
+class BinarySearch 
+{ 
+    // Returns index of x if it is present in arr[l.. r], else return -1 
+    int binarySearch(int arr[], int l, int r, int x) 
+    { 
+        //Write your code here
+        if (r >= l) {
+            int mid = l + (r - l) / 2;
+            if (arr[mid] == x) {
+                return mid;
+            }
+            if (arr[mid] > x) {
+                return binarySearch(arr, l, mid - 1, x);
+            }
+            return binarySearch(arr, mid + 1, r, x);
+        }
+        return -1;
+    } 
+  
+    // Driver method to test above 
+    public static void main(String args[]) 
+    { 
+        BinarySearch ob = new BinarySearch(); 
+        int arr[] = { 2, 3, 4, 10, 40 }; 
+        int n = arr.length; 
+        int x = 10; 
+        int result = ob.binarySearch(arr, 0, n - 1, x); 
+        if (result == -1) 
+            System.out.println("Element not present"); 
+        else
+            System.out.println("Element found at index " + result); 
+    } 
+} 
diff --git a/Exercise_5.java b/Exercise_5.java
deleted file mode 100644
index 30e82675..00000000
--- a/Exercise_5.java
+++ /dev/null
@@ -1,36 +0,0 @@
-class IterativeQuickSort { 
-    void swap(int arr[], int i, int j) 
-    { 
-	//Try swapping without extra variable 
-    } 
-  
-    /* This function is same in both iterative and 
-       recursive*/
-    int partition(int arr[], int l, int h) 
-    { 
-        //Compare elements and swap.
-    } 
-  
-    // Sorts arr[l..h] using iterative QuickSort 
-    void QuickSort(int arr[], int l, int h) 
-    { 
-        //Try using Stack Data Structure to remove recursion.
-    } 
-  
-    // A utility function to print contents of arr 
-    void printArr(int arr[], int n) 
-    { 
-        int i; 
-        for (i = 0; i < n; ++i) 
-            System.out.print(arr[i] + " "); 
-    } 
-  
-    // Driver code to test above 
-    public static void main(String args[]) 
-    { 
-        IterativeQuickSort ob = new IterativeQuickSort(); 
-        int arr[] = { 4, 3, 5, 2, 1, 3, 2, 3 }; 
-        ob.QuickSort(arr, 0, arr.length - 1); 
-        ob.printArr(arr, arr.length); 
-    } 
-} 
\ No newline at end of file
diff --git a/IterativeQuickSort.java b/IterativeQuickSort.java
new file mode 100644
index 00000000..e5a46d15
--- /dev/null
+++ b/IterativeQuickSort.java
@@ -0,0 +1,73 @@
+//Time Complexity : O(n log n)
+//Space Complexity : O(log n) in worst case and O(1) in best case
+class IterativeQuickSort 
+{ 
+    void swap(int arr[], int i, int j) 
+    { 
+	//Try swapping without extra variable 
+        arr[i] = arr[i] + arr[j];
+        arr[j] = arr[i] - arr[j];
+        arr[i] = arr[i] - arr[j];
+    } 
+  
+    /* This function is same in both iterative and 
+       recursive*/
+    int partition(int arr[], int l, int h) 
+    { 
+        //Compare elements and swap.
+        int pivot = arr[h];
+        int i = l - 1;
+        for (int j = l; j < h; j++) {
+            if (arr[j] < pivot) 
+            {
+                i++;
+                swap(arr, i, j);
+            }
+        }
+        swap(arr, i + 1, h);
+        return i + 1;
+    } 
+  
+    // Sorts arr[l..h] using iterative QuickSort 
+    void QuickSort(int arr[], int l, int h) 
+    { 
+        //Try using Stack Data Structure to remove recursion.
+        int [] stack = new int[h - l + 1];
+        int top = -1;
+        stack[++top] = l;
+        stack[++top] = h;
+        while (top >= 0) 
+        {
+            h = stack[top--];
+            l = stack[top--];
+            int pi = partition(arr, l, h);
+            if (pi - 1 > l) 
+            {
+                stack[++top] = l;
+                stack[++top] = pi - 1;
+            }
+            if (pi + 1 < h) 
+            {
+                stack[++top] = pi + 1;
+                stack[++top] = h;
+            }
+        }
+    } 
+  
+    // A utility function to print contents of arr 
+    void printArr(int arr[], int n) 
+    { 
+        int i; 
+        for (i = 0; i < n; ++i) 
+            System.out.print(arr[i] + " "); 
+    } 
+  
+    // Driver code to test above 
+    public static void main(String args[]) 
+    { 
+        IterativeQuickSort ob = new IterativeQuickSort(); 
+        int arr[] = { 4, 3, 5, 2, 1, 3, 2, 3 }; 
+        ob.QuickSort(arr, 0, arr.length - 1); 
+        ob.printArr(arr, arr.length); 
+    } 
+} 
\ No newline at end of file
diff --git a/Exercise_4.java b/MergeSort.java
similarity index 54%
rename from Exercise_4.java
rename to MergeSort.java
index 81afd3c2..1eccdc57 100644
--- a/Exercise_4.java
+++ b/MergeSort.java
@@ -1,42 +1,78 @@
-class MergeSort 
-{ 
-    // Merges two subarrays of arr[]. 
-    // First subarray is arr[l..m] 
-    // Second subarray is arr[m+1..r] 
-    void merge(int arr[], int l, int m, int r) 
-    {  
-       //Your code here  
-    } 
-  
-    // Main function that sorts arr[l..r] using 
-    // merge() 
-    void sort(int arr[], int l, int r) 
-    { 
-	//Write your code here
-        //Call mergeSort from here 
-    } 
-  
-    /* A utility function to print array of size n */
-    static void printArray(int arr[]) 
-    { 
-        int n = arr.length; 
-        for (int i=0; i<n; ++i) 
-            System.out.print(arr[i] + " "); 
-        System.out.println(); 
-    } 
-  
-    // Driver method 
-    public static void main(String args[]) 
-    { 
-        int arr[] = {12, 11, 13, 5, 6, 7}; 
-  
-        System.out.println("Given Array"); 
-        printArray(arr); 
-  
-        MergeSort ob = new MergeSort(); 
-        ob.sort(arr, 0, arr.length-1); 
-  
-        System.out.println("\nSorted array"); 
-        printArray(arr); 
-    } 
+//Time Complexity : O(n log n)
+//Space Complexity : O(log n) in worst case and O(1) in best case
+class MergeSort 
+{ 
+    // Merges two subarrays of arr[]. 
+    // First subarray is arr[l..m] 
+    // Second subarray is arr[m+1..r] 
+    void merge(int arr[], int l, int m, int r) 
+    {  
+       //Your code here  
+         int n1 = m - l + 1;
+         int n2 = r-m;
+        int L[] = new int [n1];
+        int R[] = new int [n2];
+        for(int i=0;i<n1;i++)
+        {
+            L[i] = arr[l+i];
+        }
+        for(int i=0;i<n2;i++)
+        {
+            R[i] = arr[m+1+i];
+        }
+        int i=0, j=0, k=l;
+        while(i<n1 && j<n2)
+        {
+            if(L[i] <= R[j])
+            {
+                arr[k] = L[i];
+                i++;
+            }
+            else
+            {
+                arr[k] = R[j];
+                j++;
+            }
+            k++;
+        }
+    } 
+  
+    // Main function that sorts arr[l..r] using 
+    // merge() 
+    void sort(int arr[], int l, int r) 
+    { 
+	//Write your code here
+        if(l < r)
+        {
+            int m = l + (r-l)/2;
+            sort(arr, l, m);
+            sort(arr, m+1, r);
+            merge(arr, l, m, r);
+        }
+        //Call mergeSort from here 
+    } 
+  
+    /* A utility function to print array of size n */
+    static void printArray(int arr[]) 
+    { 
+        int n = arr.length; 
+        for (int i=0; i<n; ++i) 
+            System.out.print(arr[i] + " "); 
+        System.out.println(); 
+    } 
+  
+    // Driver method 
+    public static void main(String args[]) 
+    { 
+        int arr[] = {12, 11, 13, 5, 6, 7}; 
+  
+        System.out.println("Given Array"); 
+        printArray(arr); 
+  
+        MergeSort ob = new MergeSort(); 
+        ob.sort(arr, 0, arr.length-1); 
+  
+        System.out.println("\nSorted array"); 
+        printArray(arr); 
+    } 
 } 
\ No newline at end of file
diff --git a/Exercise_2.java b/QuickSort.java
similarity index 62%
rename from Exercise_2.java
rename to QuickSort.java
index d0b5fa5f..8654070f 100644
--- a/Exercise_2.java
+++ b/QuickSort.java
@@ -1,48 +1,70 @@
-class QuickSort 
-{ 
-    /* This function takes last element as pivot, 
-       places the pivot element at its correct 
-       position in sorted array, and places all 
-       smaller (smaller than pivot) to left of 
-       pivot and all greater elements to right 
-       of pivot */
-    void swap(int arr[],int i,int j){
-        //Your code here   
-    }
-    
-    int partition(int arr[], int low, int high) 
-    { 
-   	//Write code here for Partition and Swap 
-    } 
-    /* The main function that implements QuickSort() 
-      arr[] --> Array to be sorted, 
-      low  --> Starting index, 
-      high  --> Ending index */
-    void sort(int arr[], int low, int high) 
-    {  
-            // Recursively sort elements before 
-            // partition and after partition 
-    } 
-  
-    /* A utility function to print array of size n */
-    static void printArray(int arr[]) 
-    { 
-        int n = arr.length; 
-        for (int i=0; i<n; ++i) 
-            System.out.print(arr[i]+" "); 
-        System.out.println(); 
-    } 
-  
-    // Driver program 
-    public static void main(String args[]) 
-    { 
-        int arr[] = {10, 7, 8, 9, 1, 5}; 
-        int n = arr.length; 
-  
-        QuickSort ob = new QuickSort(); 
-        ob.sort(arr, 0, n-1); 
-  
-        System.out.println("sorted array"); 
-        printArray(arr); 
-    } 
-} 
+//Time Complexity : O(n log n)
+//Space Complexity : O(log n) in worst case and O(1) in best case
+class QuickSort 
+{ 
+    /* This function takes last element as pivot, 
+       places the pivot element at its correct 
+       position in sorted array, and places all 
+       smaller (smaller than pivot) to left of 
+       pivot and all greater elements to right 
+       of pivot */
+    void swap(int arr[],int i,int j){
+        //Your code here   
+        int temp = arr[i];
+        arr[i] = arr[j];
+        arr[j] = temp;
+    }
+    
+    int partition(int arr[], int low, int high) 
+    { 
+   	//Write code here for Partition and Swap
+        int pivot = arr[high];
+        int i = low - 1;
+        for (int j = low; j < high; j++) {
+            if (arr[j] < pivot) {
+                i++;
+                swap(arr, i, j);
+            }
+        }
+        swap(arr, i + 1, high);
+        return i + 1; 
+    } 
+    /* The main function that implements QuickSort() 
+      arr[] --> Array to be sorted, 
+      low  --> Starting index, 
+      high  --> Ending index */
+    void sort(int arr[], int low, int high) 
+    {  
+            // Recursively sort elements before
+            int pi = partition(arr, low, high);
+            // partition and after partition 
+            if (low < pi - 1) {
+                sort(arr, low, pi - 1);
+            }
+            if (pi + 1 < high) {
+                sort(arr, pi + 1, high);
+            }
+    } 
+  
+    /* A utility function to print array of size n */
+    static void printArray(int arr[]) 
+    { 
+        int n = arr.length; 
+        for (int i=0; i<n; ++i) 
+            System.out.print(arr[i]+" "); 
+        System.out.println(); 
+    } 
+  
+    // Driver program 
+    public static void main(String args[]) 
+    { 
+        int arr[] = {10, 7, 8, 9, 1, 5}; 
+        int n = arr.length; 
+  
+        QuickSort ob = new QuickSort(); 
+        ob.sort(arr, 0, n-1); 
+  
+        System.out.println("sorted array"); 
+        printArray(arr); 
+    } 
+} 
diff --git a/Exercise_3.java b/SinglyLL.java
similarity index 78%
rename from Exercise_3.java
rename to SinglyLL.java
index 1f9b752a..77dcc6b2 100644
--- a/Exercise_3.java
+++ b/SinglyLL.java
@@ -1,53 +1,62 @@
-class LinkedList 
-{ 
-    Node head; // head of linked list 
-  
-    /* Linked list node */
-    class Node 
-    { 
-        int data; 
-        Node next; 
-        Node(int d) 
-        { 
-            data = d; 
-            next = null; 
-        } 
-    } 
-  
-    /* Function to print middle of linked list */
-   //Complete this function
-    void printMiddle() 
-    { 
-        //Write your code here
-	//Implement using Fast and slow pointers
-    } 
-  
-    public void push(int new_data) 
-    { 
-        Node new_node = new Node(new_data); 
-        new_node.next = head; 
-        head = new_node; 
-    } 
-
-    public void printList() 
-    { 
-        Node tnode = head; 
-        while (tnode != null) 
-        { 
-            System.out.print(tnode.data+"->"); 
-            tnode = tnode.next; 
-        } 
-        System.out.println("NULL"); 
-    } 
-  
-    public static void main(String [] args) 
-    { 
-        LinkedList llist = new LinkedList(); 
-        for (int i=15; i>0; --i) 
-        { 
-            llist.push(i); 
-            llist.printList(); 
-            llist.printMiddle(); 
-        } 
-    } 
+class LinkedList 
+{ 
+    Node head; // head of linked list 
+  
+    /* Linked list node */
+    class Node 
+    { 
+        int data; 
+        Node next; 
+        Node(int d) 
+        { 
+            data = d; 
+            next = null; 
+        } 
+    } 
+  
+    /* Function to print middle of linked list */
+   //Complete this function
+    void printMiddle() 
+    { 
+        //Write your code here
+	//Implement using Fast and slow pointers
+        Node slow = head;
+        Node fast = head;
+        if (head != null) {
+            while (fast != null && fast.next != null) {
+                fast = fast.next.next;
+                slow = slow.next;
+            }
+            System.out.println("Middle element: " + slow.data);
+        }
+    } 
+  
+    public void push(int new_data) 
+    { 
+        Node new_node = new Node(new_data); 
+        new_node.next = head; 
+        head = new_node; 
+    } 
+
+    public void printList() 
+    { 
+        Node tnode = head; 
+        while (tnode != null) 
+        { 
+            System.out.print(tnode.data+"->"); 
+            tnode = tnode.next; 
+        } 
+        System.out.println("NULL"); 
+    } 
+  
+    public static void main(String [] args) 
+    { 
+        LinkedList llist = new LinkedList(); 
+        for (int i=15; i>0; --i) 
+        { 
+            llist.push(i); 
+            llist.printList(); 
+            llist.printMiddle(); 
+        } 
+    } 
 } 
\ No newline at end of file