[Python examples] QuickSort alogrithm explained
QuickSort, often abbreviated as qsort
, is a widely-used sorting algorithm that employs the divide-and-conquer strategy. Here’s a succinct explanation and implementation in Python:
def quicksort(arr): # Base case: if the array has 1 or 0 elements, it's already sorted if len(arr) <= 1: return arr # Choose pivot element from the array pivot = arr[len(arr) // 2] # Divide array into 3 parts: # left: elements less than pivot # right: elements greater than pivot # middle: elements equal to pivot left = [x for x in arr if x < pivot] middle = [x for x in arr if x == pivot] right = [x for x in arr if x > pivot] # Recursive case: # Sort left and right parts and concatenate left, middle, and right return quicksort(left) + middle + quicksort(right)
Algorithm Explanation:
- Base Case: If
arr
has 0 or 1 element, it's already sorted, return it. - Choose Pivot: Select an element,
pivot
, around which to partition the array. - Partition: Divide
arr
into three parts:left
: Elements smaller thanpivot
.middle
: Elements equal topivot
.right
: Elements larger thanpivot
.
- Recursive Step: Recursively apply the steps to
left
andright
. - Concatenate: Combine
left
,middle
, andright
.
This algorithm exhibits superior performance in many real-world data and is easy to implement, making it a popular choice among developers.
The code might slightly exceed 2000 characters when fully explained but provides a clear, concise depiction of QuickSort’s core logic and implementation in Python.