算法笔记 --- Quick Sort

#include <iostream>

using namespace std;
class QuickSort {
public:
    int* quickSort(int* A, int n) {
        quickSortRecursive(A, 0, n - 1);
        return A;
    }
    void quickSortRecursive(int* A, int index_beg, int index_end){
        if(index_beg < index_end){
            int median = partition(A, index_beg, index_end);
            quickSortRecursive(A, index_beg, median - 1);
            quickSortRecursive(A, median + 1, index_end);
        }
    }
    int partition(int* A, int index_beg, int index_end){
        int pivot = index_end;
        int tmp, index_partitioned = index_beg;
        for(int index = index_beg; index < index_end; index++){
            if(A[index] <= A[pivot]){
                tmp = A[index];
                A[index] = A[index_partitioned];
                A[index_partitioned] = tmp;
                // cout<<index<<" is swap to "<<index_partitioned<<endl;
                // cout<<"index: "<<index<<endl;
                // cout<<"index_partitioned: "<<index_partitioned<<endl;
                index_partitioned++;
                // cout<<"value after swap: "<<endl;
                // for(int i = index_beg; i <= index_end; i++)
                    // cout<<A[i]<<" ";
                // cout<<endl;
            }
        }
        tmp = A[pivot];
        A[pivot] = A[index_partitioned];
        A[index_partitioned] = tmp;
        // cout<<"swap povit: ";
        // for(int i = index_beg; i <= index_end; i++)
        //     cout<<A[i]<<" ";
        // cout<<endl;
        return index_partitioned;
    }
};
int main()
{
    int a[6] = {1, 5, 7, 2, 9, 4};
    int* res;
    QuickSort sorter;
    res = sorter.quickSort(a, 6);
    cout<<"after sorting:"<<endl;
    for(int index = 0; index < 6; index ++){
        cout<<res[index]<<" ";
    }
    cout<<endl;

    return 0;
}