quick sort 实现

快排这个算法早就已经学过，一般直接使用STL里的sort()就可以了，粗略的想一下，貌似觉得非常的简单。就算这样，在自己具体动手去实现的时候还是遇到一些问题，比如排序的具体流程，怎么尽量减少时间与空间的复杂度以及使用模板类，及比较函数的传入等。

最后实现了跟里sort基本一样的功能，C++代码及测试如下：

#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;



int cnt = 0;
template
void mySort(T *__begin, T *__end)
{
    cnt++;
    if (__end - __begin <= 1) return;
    T mid = *(__begin + (__end - __begin - 1)/2);
    T *begin = __begin, *end = __end - 1;
    while (begin <= end)
    {
        while (begin<=end && *begin < mid)
        {
            begin++;
        }
        while (begin <=end && mid < *end)
        {
            end--;
        }
        if (begin <= end)
        {
            swap(*begin, *end);
            begin++;
            end--;
        }
    }
    mySort(__begin, end+1);
    mySort(begin, __end);
}

template
void mySort(T *__begin, T *__end, Comp *cmp)
{
    cnt++;
    if (__end - __begin <= 1) return;
    T mid = *(__begin + (__end - __begin - 1) / 2);
    T *begin = __begin, *end = __end - 1;
    while (begin <= end)
    {
        while (begin <= end && cmp(*begin, mid))
        {
            begin++;
        }
        while (begin <= end && cmp(mid, *end))
        {
            end--;
        }
        if (begin <= end)
        {
            swap(*begin, *end);
            begin++;
            end--;
        }
    }
    mySort(__begin, end + 1, cmp);
    mySort(begin, __end, cmp);

}

bool comp(int a, int b)
{
    return a < b;
}


struct node
{
    int x, y;
    node()
    {
        x = rand();
        y = rand();
    }
    bool operator < (node a)
    {
        if (a.x == x) return y < a.y;
        return x < a.x;
    }
};

bool cmp2(node a, node b)
{
    return a.x > b.x;
}

int main()

{
    const int N = 128;
    int go[N];
    srand(rand());
    for (int i = 0; i < N; i++) go[i] = rand();
    for (int i = 0; i < N; i++) cout << i << '-' << go[i] << "  ";
    cout << endl;

    sort(go, go + N, comp);
    mySort(go, go + N, comp);

    

    for (int i = 0; i < N; i++) cout << i << '-' << go[i] << "  ";
    cout << endl <<"Sort() function called "<< cnt << " times!"<< endl;
    for (int i = 1; i < N; i++) if (go[i] < go[i - 1]) cout<