JavaScript Exercises: Remove duplicates from a given stack

JavaScript Stack: Exercise-9 with Solution

Remove Duplicates from Stack

Write a JavaScript program to remove duplicates from a given stack.

Sample Solution:

JavaScript Code:

class Stack {
  constructor() {
    this.items = [];
  }

  push(element) {
    this.items.push(element);
  }
  pop() {
    if (this.isEmpty())
      return "Underflow";
    return this.items.pop();
  }
  peek() {
    if (this.isEmpty())
      return "No elements in Stack";
    return this.items[this.items.length - 1];
  }
  isEmpty() {
    return this.items.length === 0;
  }
removeDuplicates() {
    const uniqueItems = [];
    const seen = new Set();
    for (let i = 0; i < this.items.length; i++) {
      const currentItem = this.items[i];
      if (!seen.has(currentItem)) {
        uniqueItems.push(currentItem);
        seen.add(currentItem);
      }
    }
    this.items = uniqueItems;
  }
displayStack(stack) {
  console.log("Stack elements are:");
  let str = "";
  for (let i = 0; i < stack.items.length; i++)
    str += stack.items[i] + " ";
  return str.trim();
 }        
}
console.log("Initialize a stack:")
let stack = new Stack();
console.log("Input some elements on the stack:")
stack.push(1);
stack.push(6);
stack.push(3);
stack.push(2);
stack.push(5);
stack.push(6); 
console.log(stack.displayStack(stack));
stack.removeDuplicates();
console.log("After removing duplicates from the said stack:");
console.log(stack.displayStack(stack));
console.log("Input two more elements on the stack:")
stack.push(1);
stack.push(6);
console.log(stack.displayStack(stack));
stack.removeDuplicates();
console.log("After removing duplicates from the said stack:");
console.log(stack.displayStack(stack));

Sample Output:

Initialize a stack:
Input some elements on the stack:
Stack elements are:
1 6 3 2 5 6
After removing duplicates from the said stack:
Stack elements are:
1 6 3 2 5
Input two more elements on the stack:
Stack elements are:
1 6 3 2 5 1 6
After removing duplicates from the said stack:
Stack elements are:
1 6 3 2 5

Flowchart:

Live Demo:

See the Pen javascript-stack-exercise-8 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that removes duplicate elements from a stack and retains only the first occurrence of each item.
• Write a JavaScript function that uses an auxiliary stack to filter out duplicate values while preserving order.
• Write a JavaScript function that iterates over a stack and builds a new stack free of duplicate entries.
• Write a JavaScript function that checks for duplicates in a stack using a hash table and removes them in a single pass.

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• JavaScript Stack Exercises Home ↩
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