Stack

Push & Pop

What is Stack Push & Pop?

Push and pop are the only two moves a stack really needs. Push adds a value on top, pop takes the top value back off, and because of that, whatever went on last is always the first thing to come off: that's the LIFO (Last In, First Out) rule in action.

Push Operation

Adds an element to the top of the stack.

Example: Pushing elements onto a stack

  1. Start with empty stack
    empty
  2. Push 5
    5top
  3. Push 3
    53top
  4. Push 7
    537top
  • Time Complexity: O(1)
  • Space Complexity: O(1)

Pop Operation

Removes and returns the topmost element from the stack.

Example: Popping elements from a stack

  1. Current stack, 7 on top
    537top
  2. Pop → returns 7
    53top
  3. Pop → returns 3
    5top
  4. Pop → returns 5
    empty
  • Time Complexity: O(1)
  • Space Complexity: O(1)

Time Complexity Analysis

Stack Underflow & Overflow

  • Stack Underflow: Trying to pop from an empty stack
  • Stack Overflow: Trying to push to a full stack (in fixed-size implementations)

Real-world Applications

  • Function call management in programming languages (call stack)
  • Undo/Redo operations in text editors
  • Back/Forward navigation in web browsers
  • Expression evaluation and syntax parsing
  • Memory management

Push and Pop operations are fundamental to stack functionality. While simple to implement, stacks are powerful data structures used in many algorithms and system designs.

Daily DSA Challenge by Scale Engineer

Visualize the LIFO (Last In, First Out) principle

Stack is empty

Test Your Knowledge before moving forward!

Stack Quiz Challenge

How it works:

  • +1 point for each correct answer
  • 0 points for wrong answers
  • Earn stars based on your final score (max 5 stars)

Stack Push & Pop Implementation

// Stack Implementation with Push/Pop in JavaScript
class Stack {
  constructor() {
    this.items = [];
    this.top = -1;
    this.MAX_SIZE = 10;
  }

  // Push operation
  push(element) {
    if (this.top >= this.MAX_SIZE - 1) {
      console.log("Stack Overflow");
      return;
    }
    this.items[++this.top] = element;
    console.log(`Pushed: ${element}`);
  }

  // Pop operation
  pop() {
    if (this.top < 0) {
      console.log("Stack Underflow");
      return -1;
    }
    const element = this.items[this.top--];
    console.log(`Popped: ${element}`);
    return element;
  }

  // Display stack
  display() {
    console.log("Current Stack:", this.items.slice(0, this.top + 1));
  }
}

// Usage
const stack = new Stack();
stack.push(10);
stack.push(20);
stack.push(30);
stack.display();
stack.pop();
stack.display();

Done With the Learning

Mark Stack : Push & Pop as done and view it on your dashboard

Explore other operations

Peek

Is Empty

Is Full