Quicksort Algorithm

Efficient O(n log n) sorting algorithm using divide-and-conquer. Sorts array in-place with good average performance.

Python7/16/2025

#algorithms#sorting#python

Python

def quicksort(arr, low=0, high=None):
    if high is None:
        high = len(arr) - 1
    
    if low < high:
        pi = partition(arr, low, high)
        quicksort(arr, low, pi - 1)
        quicksort(arr, pi + 1, high)
    
    return arr

def partition(arr, low, high):
    pivot = arr[high]
    i = low - 1
    
    for j in range(low, high):
        if arr[j] <= pivot:
            i += 1
            arr[i], arr[j] = arr[j], arr[i]
    
    arr[i + 1], arr[high] = arr[high], arr[i + 1]
    return i + 1

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