Implementing the QuickSort Algorithm in C++

QuickSort is based on the divide-and-conquer method with an average time complexity of O(n log n), widely used in practical applications. Its core idea involves selecting a pivot element, partitioning the array into two parts (elements less than and greater than the pivot), and then recursively sorting the subarrays. The Lomuto partition scheme is adopted, where the rightmost element serves as the pivot. By traversing the array, elements smaller than the pivot are moved to the left, and finally, the pivot is swapped to its correct position (at index i+1). The C++ implementation includes a partition function and a recursive main function (quickSort). The partitioning operation is performed on the original array to achieve in-place sorting. The recursion terminates when the subarray length is ≤1 (i.e., left ≥ right). The average time complexity is O(n log n), while the worst-case complexity is O(n²) (e.g., when sorting an already sorted array with the leftmost/rightmost element as the pivot). This can be optimized by randomly selecting the pivot. Key features: in-place sorting with no additional space required, clear recursion termination conditions, average efficiency, and optimizable worst-case performance. QuickSort is a frequently tested and used algorithm in interviews and development. Mastering its partitioning logic and recursive thinking is crucial for understanding efficient sorting algorithms.