经典排序算法——快速排序

[1,2,3,5,2,3],6

[1,2,2,3,3,5]

class QuickSort {
public:
    int* quickSort(int* A, int n) {
        // write code here
        if(A==NULL || n<2)
            return A;
        process(A,0,n-1);
        return A;
    }
    
    int* process(int* A, int low,int high) {
        if (low < high) {
            int mid = partition(A, low, high);
            process(A, low, mid-1);//对A[low...mid-1]进行递归操作排序
            process(A, mid + 1, high);//对A[mid+1...high]进行递归操作排序
        }
        return A;
    }
    
    int partition(int* A,int low,int high){ //快排算法的划分过程，将数组划分为左右两个子数组
        int pivot = A[low];
        int i = low;
        int j = high;
        if (low < high) 
        {
            while (i < j) 
            {
                while (i < j && pivot <= A[j])  j--;//找到比基准数小的元素
                if (i < j)  A[i] = A[j];
                while (i < j && pivot >= A[i])  i++;//找到比基准数大的元素
                if (i < j)  A[j] = A[i];
            }
            A[i] = pivot;
        }
        return i;
    }
};