Quicksort (In-Place)

Description: Sorts an array of integers using the standard in-place version of quicksort. For simplicity the right most index is chosen as pivot. If you wish to alter this, simply choose a different pivot and swap it to the end.
Tested Platform: Java SE 19, Windows 10
Language: Java
// Takes an array, along with the left and right indexes
// Partitions it and then recursively calls itself on 
// left and right halfs of array.
public static int[] quickSort(int[] data, int left, int right){
    if (left < right) {
        int i = partition(data,left,right);
        quickSort(data, left, i - 1);
        quickSort(data, i + 1 , right);    
    return data;
public static int partition(int[] data, int left, int right){
    // Select a pivot value in the right most index
    int pivot = data[right];
    int i = left;
    int temp;
    for (int j = left; j < right; j++) {
        if (data[j] < pivot) {
            // Swap i with j, increment i
            temp = data[i];
            data[i] = data[j];
            data[j] = temp;
    // Move pivot to last index "i"
    temp = data[i];
    data[i] = data[right];
    data[right] = temp;
    return i;

Posted: March 20, 2023

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