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# Quicksort Cheatsheet

## Overview

- Quicksort is a divide-and-conquer sorting algorithm.
- It works by selecting a 'pivot' element from the array and partitioning the other elements into two sub-arrays, according to whether they are less than or greater than the pivot.
- The sub-arrays are then sorted recursively.

## Algorithm

def quicksort(arr, start, end):

if start < end:

# Partition the array

pivot_index = partition(arr, start, end)

# Sort the left sub-array

quicksort(arr, start, pivot_index - 1)

# Sort the right sub-array

quicksort(arr, pivot_index + 1, end)

def partition(arr, start, end):

# Select the pivot element

pivot = arr[end]

# Initialize the pivot index

pivot_index = start

# Partition the array

for i in range(start, end):

if arr[i] < pivot:

arr[i], arr[pivot_index] = arr[pivot_index], arr[i]

pivot_index += 1

# Move the pivot element to its final position

arr[pivot_index], arr[end] = arr[end], arr[pivot_index]

# Return the pivot index

return pivot_index

## Time Complexity

-  Worst-case performance: O(n^2)
-  Best-case performance: O(n log n)
-  Average-case performance: O(n log n)

## Resources

- [Quicksort Wikipedia](https://en.wikipedia.org/wiki/Quicksort)
- [GeeksforGeeks: Quicksort](https://www.geeksforgeeks.org/quick-sort/)
- [Visualgo: Quicksort](https://visualgo.net/en/sorting)