Quick Sort Partition Lomuto and Hoare in DSA Javascript - Build from Scratch

Quick Sort Partition: Lomuto and Hoare

📖 Scenario: You are working on sorting a list of numbers to organize your data efficiently. Quick Sort is a fast sorting method that uses a step called partitioning to arrange elements around a pivot.There are two popular ways to partition: Lomuto and Hoare. Understanding both helps you see how Quick Sort works under the hood.

🎯 Goal: You will create two functions in JavaScript: one for Lomuto partition and one for Hoare partition. Then, you will apply these to a sample array and print the partitioned array and pivot index after each method.

📋 What You'll Learn

Create an array called arr with the exact numbers [8, 3, 1, 7, 0, 10, 2]

Create a variable high set to the last index of the array

Write a function lomutoPartition that partitions the array using Lomuto's method

Write a function hoarePartition that partitions the array using Hoare's method

Print the array and pivot index after applying each partition method

💡 Why This Matters

🌍 Real World

Sorting is used everywhere: organizing data, searching faster, and improving software speed.

💼 Career

Understanding Quick Sort and its partition methods is essential for software engineers and data scientists to optimize algorithms.

1

Create the initial array

Create an array called arr with these exact numbers: [8, 3, 1, 7, 0, 10, 2]

DSA Javascript

# Your code here

Hint

Use const arr = [8, 3, 1, 7, 0, 10, 2]; to create the array.

2

Set the high index variable

Create a variable called high and set it to the last index of arr using arr.length - 1

DSA Javascript

const arr = [8, 3, 1, 7, 0, 10, 2];
# Your code here

Hint

Use const high = arr.length - 1; to get the last index.

3

Write the Lomuto partition function

Write a function called lomutoPartition that takes array, low, and high as parameters and partitions the array using Lomuto's method. Use the last element as pivot. Return the pivot index after partitioning.

DSA Javascript

const arr = [8, 3, 1, 7, 0, 10, 2];
const high = arr.length - 1;

# Your code here

Hint

Use the last element as pivot. Move smaller elements left, then place pivot after them.

4

Write the Hoare partition function and print results

Write a function called hoarePartition that takes array, low, and high as parameters and partitions the array using Hoare's method. Use the first element as pivot. Return the partition index. Then, call both lomutoPartition and hoarePartition on copies of arr with low = 0 and high as defined. Print the array and pivot index after each partition in this exact format:
console.log('Lomuto partition index:', lomutoIndex);
console.log('Array after Lomuto partition:', lomutoArr);
console.log('Hoare partition index:', hoareIndex);
console.log('Array after Hoare partition:', hoareArr);

DSA Javascript

const arr = [8, 3, 1, 7, 0, 10, 2];
const high = arr.length - 1;

function lomutoPartition(array, low, high) {
    const pivot = array[high];
    let i = low - 1;
    for (let j = low; j < high; j++) {
        if (array[j] <= pivot) {
            i++;
            [array[i], array[j]] = [array[j], array[i]];
        }
    }
    [array[i + 1], array[high]] = [array[high], array[i + 1]];
    return i + 1;
}

# Your code here

Hint

Use the first element as pivot for Hoare. Move pointers inward and swap elements until pointers cross.

Print results exactly as shown.