快速排序

1. 快速排序是通过递归实现。

2. 快速排序先选取基准值base，从两端向中间遍历，通过一次遍历将序列调整为
   [小于base的序列，base，大于base的序列] ------以从小到大为例

3. 再通过递归，分别对小于base的序列和大于base的序列进行快速排序，最终完成排序。

Algorithm	Time Complexity			Space Complexity
	Best	Average	Worst	Worst
Quicksort	Ω(n log(n))	Θ(n log(n)	O(n^2)	O(log(n))

//c++
void quickSort(vector&nums, int left, int right){
    if (left > right) return;

    int low = left;
    int high = right;
    int base = nums[left];
    
    while (low < high){
        while (nums[high] >= base and low < high){
            high--;
        }
        nums[low] = nums[high];
        
        while (nums[low] <= base and low < high){
            low++;
        }
        nums[high] = nums[low];
    }
    nums[low] = base;
    
    quickSort(nums, left, low-1);
    quickSort(nums, high+1, right);
}