Implement Stack using Array, Implementing Stack using Linked List and Implement Singly Linked List

Exercise_1.java

@@ -8,28 +8,56 @@ class Stack {
     boolean isEmpty() 
     { 
         //Write your code here 
+        return (top == 0);
     } 
 
     Stack() 
     { 
         //Initialize your constructor 
+        top = 0;
     } 
 
     boolean push(int x) 
     { 
         //Check for stack Overflow
         //Write your code here
+        if(top == MAX)
+        {
+            System.out.println("Stack Overflow");
+            return false;
+        }
+
+        top += 1;
+        a[top] = x;
+        return true;
     } 
 
     int pop() 
     { 
         //If empty return 0 and print " Stack Underflow"
         //Write your code here
+        if(top == 0)
+        {
+            System.out.println("Stack Underflow");
+            return 0;
+        }
+
+        int ele = a[top];
+        top -= 1;
+        return ele;
+
     } 
 
     int peek() 
     { 
         //Write your code here
+        if(top == 0)
+        {
+            System.out.println("Stack Underflow");
+            return 0;
+        }
+
+        return a[top];
     } 
 } 
 

Exercise_2.java

@@ -9,30 +9,65 @@ static class StackNode {
         StackNode(int data) 
         { 
             //Constructor here 
+            this.data = data;
+            this.next = null;
         } 
     } 
+
+    public StackAsLinkedList()
+    {
+        this.root = new StackNode(Integer.MIN_VALUE);
+    }
 
 
     public boolean isEmpty() 
     { 
-        //Write your code here for the condition if stack is empty. 
+        //Write your code here for the conditi on if stack is empty. 
+        if(root.data == Integer.MIN_VALUE)
+        {
+            return true;
+        }
+
+        return false;
     } 
 
     public void push(int data) 
     { 
         //Write code to push data to the stack. 
+        StackNode temp = new StackNode(data);
+        temp.next = root;
+        root = temp;
     } 
 
     public int pop() 
     { 	
 	//If Stack Empty Return 0 and print "Stack Underflow"
         //Write code to pop the topmost element of stack.
 	//Also return the popped element 
+        if(root.data == Integer.MIN_VALUE)
+        {
+            System.out.println("Stack Underflow");
+            return 0;
+        }
+
+        StackNode temp = root;
+        int ele = temp.data;
+        root = root.next;
+        temp.next = null;
+        return ele;
+
     } 
 
     public int peek() 
     { 
         //Write code to just return the topmost element without removing it.
+        if(root.data == Integer.MIN_VALUE)
+        {
+            System.out.println("Stack Underflow");
+            return 0;
+        }
+
+        return root.data;
     } 
 
 	//Driver code

Exercise_3.java

@@ -18,22 +18,43 @@ static class Node {
         Node(int d) 
         { 
             //Write your code here 
+            this.data = d;
+            this.next = null;
         } 
     } 
-  
+
     // Method to insert a new node 
     public static LinkedList insert(LinkedList list, int data) 
     { 
         // Create a new node with given data 
+        Node newNode = new Node(data);
 
         // If the Linked List is empty, 
         // then make the new node as head 
+        if(list.head == null)
+        {
+            list.head = newNode;
+        }
 
-            // Else traverse till the last node 
-            // and insert the new_node there 
-
-            // Insert the new_node at last node 
+        // Else traverse till the last node 
+        // and insert the new_node there 
+        // Insert the new_node at last node 
         // Return the list by head 
+        else 
+        {
+            Node temp = list.head;
+
+            while(temp.next != null)
+            {
+                temp = temp.next;
+            }
+
+            temp.next = newNode;
+
+        }
+
+        return list;
+
 
     } 
 
@@ -42,9 +63,24 @@ public static void printList(LinkedList list)
     {  
         // Traverse through the LinkedList 
 
-            // Print the data at current node 
-
-            // Go to next node 
+        // Print the data at current node 
+
+        // Go to next node 
+
+        if(list == null || list.head == null)
+        {
+            System.out.println("The linked list is empty");
+            return;
+        }
+
+        Node temp = list.head;
+
+        while(temp!=null)
+        {
+            System.out.print(temp.data + " ");
+            temp = temp.next;
+        }
+
     } 
 
     // Driver code