Implement Stack Using Linked List - The Coding Shala

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 In this post, we will learn how to Implement Stack Using Linked List and will write a Java Program for the same.

Implement Stack using Linked List

We will implement Stack operations using LinkedList. If we implement using a linked list then the stack can grow and shrink dynamically but it requires extra memory because of pointers involvement.

Java Program: 

class MyStack {
    
    Node root;
    
    //linked list node
    class Node {
        int data;
        Node next;
        
        Node(int data) {
            this.data = data;
        }
    }
 
    boolean isEmpty()
    {
        return root == null;
    }
 
    void push(int x)
    {
        Node newNode = new Node(x);
        
        //if stack is empty 
        //make this as root node
        if(root == null) {
            root = newNode;
        } else {
            //add new Node at the head
            Node tmp = root;
            newNode.next = tmp;
            root = newNode;
        }
    }
 
    int pop()
    {
        int res = -1;
        
        if(root == null) {
            //empty stack;
            return -1;
        } else {
            res = root.data;
            root = root.next;
        }
        return res;
    }
 
    int peek()
    {
        if (root == null) {
            //stack underflow
            return -1;
        }
        else {
            int x = root.data;;
            return x;
        }
    }
}

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