快速排序

其实libc中有qsort函数的，用于数组型数据排序还是很好的。

话说，好久没用过排序算法了……

工作需要，就自己重新写了一个。用[0]作为分界。

/* 用[0]作为分界 
 * 0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15
 *
 * 18 35 27 19 05 34 28 67 23 17 45 98 06 18 43 24
 *    06                               35
 *       17                   27
 *          05 19
 * 05       18
 * 05 06 17 18 19 34 28 67 23 27 45 98 35 18 43 24
 * 05 06 17
 *    06 17
 *       17
 *             19 34 28 67 23 27 45 98 35 18 43 24
 *                18                      34
 *             18 19
 *             18 19 28 67 23 27 45 98 35 34 43 24
 *             18
 *                   28 67 23 27 45 98 35 34 43 24
 *                      24                      67
 *                   27       28
 *                   27 24 23 28 45 98 35 34 43 67
 *                   27 24 23
 *                   23    27
 *                   23 24 27
 *                   23 24
 *                      24
 *                               45 98 35 34 43 67
 *                                  43       98
 *                               34       45
 *                               34 43 35 45 98 67
 *                               34 43 35
 *                                  43 35
 *                                  35 43
 *                                           98 67
 *                                           67 98
 * 05 06 17 18 18 19 23 24 27 28 34 35 43 45 67 98
 * */

#include <stdio.h>
void *buf_getitem(void *buf, int i)
{
    int *buf_local = buf;
    return &buf_local[i];
}
void buf_swap(void *buf, int i, int j)
{
    int *buf_local = buf;
    int temp = buf_local[i];
    buf_local[i] = buf_local[j];
    buf_local[j] = temp;
}
int buf_compare(void *buf, int i, int j)
{
    int *buf_local = buf;
    if(buf_local[i] < buf_local[j])
        return -1;
    else if(buf_local[i] > buf_local[j])
        return 1;
    else
        return 0;
}
void quick_sort(void *buf,
        void (*swap)(void *buf, int i, int j),
        int (*compare)(void *buf, int i, int j),// 1: [i] > [j];-1:[i] < [j]
        int len)
{
    if(len < 2)
        return;
    if(len == 2)
    {
        if(compare(buf, 0,1) > 0)
            swap(buf, 0,1);
        return;
    }
    int i = 1;
    int j = len - 1;
    while(i < j)
    {
        if(compare(buf, i,0) < 0)
        {
            i++;
            continue;
        }
        if(compare(buf, j,0) >= 0)
        {
            j--;
            continue;
        }
        swap(buf, i, j);
    }

    if(j == 1)            // [0]后的数据都大于[0]
        quick_sort(buf_getitem(buf, 1), buf_swap, buf_compare, len - j);
    else if(j == len - 1)        // [0]后的数据都小于[0]
    {
　　　　 if(compare(buf, 0, j) > 0)
            swap(buf, 0, j);
        quick_sort(buf, swap, compare, j);
    }
    else
    {
        swap(buf, 0, j - 1);
        quick_sort(buf, swap, compare, j - 1);
        quick_sort(buf_getitem(buf, j), swap, compare, len - j);
    }
}

int main()
{
    int buf[16] = {    18,35,27,19,
            5,34,28,67,
            23,17,45,98,
            6,18,43,24};
    quick_sort(buf, buf_swap, buf_compare, 16);
    for(int k = 0; k < 16; k++)
        printf("%02d ",buf[k]);
    printf("\n");
    return 0;
}