Quick Sort: How to Choose the Pivot in Quick Sort? A Diagram of the Partition Process

Quick sort is based on the divide and conquer method, with the core being the selection of a pivot and partition. The choice of pivot affects efficiency: selecting the leftmost or rightmost element can lead to degradation on sorted arrays (O(n²)), while choosing the middle element results in slightly worse balance. The median-of-three method (median of the first, middle, and last elements) is most recommended as it avoids extreme cases. Partitioning is achieved by moving left and right pointers to place the pivot in its correct position, ensuring all elements to the left are smaller and all to the right are larger, followed by recursive sorting of the subarrays. With an average time complexity of O(n log n), quick sort is a highly efficient sorting algorithm commonly used in engineering.