Queue • Core Implementation

Queue using Arrays

Implementing a basic Queue using a statically sized array. We use two pointers, `front` and `rear`, to track the boundaries of the queue.

Try Interactive Simulator

Two Pointers

`Front` tracks the element to be popped. `Rear` tracks the element that was just pushed. Initially, both are `-1`.

The Flaw

As you push and pop, both pointers move to the right. Eventually, `rear` hits the end of the array. Even if there is empty space at the beginning (from popped elements), you can't use it! This is called "False Overflow".

The Fix

This massive flaw in standard Array Queues is exactly why the Circular Queue was invented, which wraps the pointers back to 0 using modulo arithmetic.

Code Tracker

:::

1let front = -1, rear = -1;

2function push(x) {

3 if (rear === size - 1) return 'Overflow';

4 if (front === -1) front = 0;

5 rear++;

6 arr[rear] = x;

7}

8function pop() {

9 if (front === -1 || front > rear) return 'Underflow';

10 let val = arr[front];

11 front++;

12 return val;

13}

Queue Arrays

Queue Arrays

Queue using Arrays

Two Pointers

The Flaw

The Fix

Queue using Arrays

Two Pointers

The Flaw

The Fix