Objective: Write an algorithm to implement Stack using Linked List.
If you do not know about then for starters its abstract data type in which follows the principle of LIFO (Last-In-First-Out) which means the data goes in last comes out first to read about in detail please read this link Stack
Approach:
Solution is quite simple, Earlier we have seen an article “Linked List Implementation“, we need to make some changes to make it work as Stack.
Stack Operations:
Push() : Insert the element into linked list at the beginning and increase the size of the list. O(1) operation.
Pop() : Return the element first node from the linked list and move the head pointer to the second node. Decrease the size of the list. O(1) operation.
getSize(): Return the size of linked list.
displayStack(): Print the linked list.
Complete Code:
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| public class StackUsingLinkedList { | |
| Node head= null; | |
| int size =0; | |
| public void push(int data){ | |
| Node x = new Node(data); | |
| if(getSize()==0){ | |
| head = x; | |
| }else{ | |
| //add the Node at the start of a Linked List | |
| Node temp = head; | |
| x.next = temp; | |
| head = x; | |
| } | |
| System.out.println("Element "+ data + " is pushed into Stack"); | |
| size++; | |
| } | |
| public int pop(){ | |
| if(getSize()==0){ | |
| System.out.println("Stack is Empty"); | |
| return –1; | |
| }else{ | |
| Node temp = head; | |
| head = head.next; | |
| size—; | |
| return temp.data; | |
| } | |
| } | |
| public void printStack(){ | |
| Node curr = head; | |
| while(curr!=null){ | |
| System.out.print(curr.data + " "); | |
| curr = curr.next; | |
| } | |
| System.out.println(); | |
| } | |
| public int getSize(){ | |
| return size; | |
| } | |
| public static void main(String[] args) { | |
| StackUsingLinkedList stck = new StackUsingLinkedList(); | |
| stck.push(1); | |
| stck.push(2); | |
| stck.push(4); | |
| stck.printStack(); | |
| System.out.println("Pop out element " + stck.pop()); | |
| stck.printStack(); | |
| } | |
| } | |
| class Node{ | |
| int data; | |
| Node next; | |
| public Node(int data){ | |
| this.data = data; | |
| } | |
| } |
Output:
Element 1 is pushed into Stack Element 2 is pushed into Stack Element 4 is pushed into Stack 4 2 1 Pop out element 4 2 1
Note: Also read, Track the Maximum Element in a Stack. This problem was asked in Yahoo in Software Engineer position.