Quick Sort is a highly efficient, comparison-based sorting algorithm that uses a divide-and-conquer strategy. It was developed by Tony Hoare in 1959 and is still one of the most widely used sorting algorithms.

Quick Sort works by:

1. Selecting a 'pivot' element from the array
2. Partitioning other elements into two sub-arrays according to whether they are less than or greater than the pivot
3. Recursively sorting the sub-arrays

• Best Case: O(n log n)
• Average Case: O(n log n)
• Worst Case: O(n²)

• O(log n) - due to the recursive call stack

• Fast in practice
• In-place sorting (requires small additional space)
• Cache friendly
• Can be easily modified for different types of data

• Unstable sort (doesn't preserve relative order of equal elements)
• O(n²) worst-case complexity
• Not adaptive (performance doesn't improve with partially sorted arrays)

Quick Sort is particularly useful when:

• You need a fast, general-purpose sorting algorithm
• Memory space is a concern
• Average-case performance is more important than worst-case guarantees
• Random access to elements is efficient (like in arrays)

• The choice of pivot can significantly affect performance
• Common pivot selection strategies include:
  • First element
  • Last element
  • Middle element
  • Random element
  • Median-of-three

• Quick Sort on Wikipedia