Quick Sort Algorithm in DSA Javascript - Build from Scratch

Quick Sort Algorithm

📖 Scenario: You have a list of numbers that you want to sort from smallest to largest. Quick Sort is a fast way to do this by dividing the list into smaller parts and sorting each part.

🎯 Goal: Build a Quick Sort function in JavaScript that sorts an array of numbers in ascending order.

📋 What You'll Learn

Create an array called numbers with the exact values: [8, 3, 7, 6, 2, 5, 4, 1]

Create a variable called pivotIndex and set it to 0

Write a function called quickSort that takes an array and returns a sorted array using the Quick Sort algorithm

Print the sorted array returned by quickSort(numbers)

💡 Why This Matters

🌍 Real World

Sorting is used in many apps like organizing contacts, searching data quickly, or arranging products by price.

💼 Career

Understanding Quick Sort helps in coding interviews and building efficient software that handles large data.

1

Create the initial array

Create an array called numbers with these exact values: [8, 3, 7, 6, 2, 5, 4, 1]

DSA Javascript

// Create the array called numbers with the given values
// Your code here

Hint

Use const numbers = [8, 3, 7, 6, 2, 5, 4, 1]; to create the array.

2

Set the pivot index

Create a variable called pivotIndex and set it to 0

DSA Javascript

const numbers = [8, 3, 7, 6, 2, 5, 4, 1];
// Create the variable pivotIndex and set it to 0
// Your code here

Hint

Use let pivotIndex = 0; to create the variable.

3

Write the Quick Sort function

Write a function called quickSort that takes an array arr and returns a sorted array using the Quick Sort algorithm. Use pivotIndex as the pivot position inside the function.

DSA Javascript

const numbers = [8, 3, 7, 6, 2, 5, 4, 1];
let pivotIndex = 0;
// Write the quickSort function below
// Your code here

Hint

Use recursion to sort the left and right parts around the pivot.

4

Print the sorted array

Print the sorted array returned by quickSort(numbers) using console.log

DSA Javascript

const numbers = [8, 3, 7, 6, 2, 5, 4, 1];
let pivotIndex = 0;

function quickSort(arr) {
    if (arr.length <= 1) {
        return arr;
    }
    pivotIndex = 0;
    const pivot = arr[pivotIndex];
    const left = [];
    const right = [];
    for (let i = 1; i < arr.length; i++) {
        if (arr[i] < pivot) {
            left.push(arr[i]);
        } else {
            right.push(arr[i]);
        }
    }
    return [...quickSort(left), pivot, ...quickSort(right)];
}
// Print the sorted array below
// Your code here

Hint

Use console.log(quickSort(numbers)); to print the sorted array.