Quick Sort:
Time complexity: best case O(n*lgn), worst case O(n^2)
Space complexity: Best case O(lgn) -> call stack height
Worse case O(n^2) -> call stack height
Merge Sort
Time complexity: always O(n*lgn) because we always divide the array in halves.
Space complexity: O(lgn + n)
原文：https://www.cnblogs.com/beiyeqingteng/p/11489565.html