快速排序

选左侧第一个数为基准数，从右侧开始找一个比基准数小的数，从左侧开始找一个比其大的数，二者调换，再接着找，直到两向相遇，则将相遇点的数据与基准数调换；接着对基准数两侧的数据进行与上述相同的操作，进行递归处理。

    void fastSort(vector<int>& nums,int left,int right){
        if(left>=right) return;
        if(nums.size()<=1) return;
        int pilot = nums[left];
        int leftIndex = left;
        int rightIndex = right;
        while(leftIndex<rightIndex){
            while(leftIndex<rightIndex){
                if(pilot<=nums[rightIndex]) rightIndex--;
                else{
                    nums[leftIndex] = nums[rightIndex];
                    leftIndex++;
                    break;
                }
            }
            while(leftIndex<rightIndex){
                if(pilot>=nums[leftIndex]) leftIndex++;
                else{
                    nums[rightIndex] = nums[leftIndex];
                    rightIndex--;
                    break;
                }
            }
        }
        nums[leftIndex] = pilot;
        fastSort(nums,left,leftIndex-1);
        fastSort(nums,rightIndex+1,right);
    }