qsort2.c

自己做的常用库和实现的数据结构。public domain.

#include <stdio.h>
#include <stddef.h>

int main(void)
{
    int keys[] = { 5, 8, 9, 15, -18, 150, 0, 55, -5, -108, 100 };
    int i;
    const int keys_size = (sizeof keys) / (sizeof *keys);
    /* prototype */
    void my_qsort(int v[], int left, int right);
   
    my_qsort( keys, 0, keys_size - 1 );
    for ( i = 0; i < keys_size; ++i ) {
        printf("%d ", keys[i]);
    }
    return 0;
}

/* my_qsort:  sort v[left]...v[right] into increasing order */
void my_qsort(int v[], int left, int right)
{
   int i, last;
   /* prototype */
   void my_swap(int v[], int i, int j);

   if (left >= right) /* do nothing if array contains */
       return;        /* fewer than two elements */
   my_swap(v, left, (left + right)/2); /* move partition elem */
   last = left;                        /* to v[0] */
   for (i = left + 1; i <= right; i++) /* partition */
       if (v[i] < v[left])
           my_swap(v, ++last, i);
   my_swap(v, left, last);            /* restore partition elem */
   my_qsort(v, left, last-1);
   my_qsort(v, last+1, right);
}

/* my_swap:  interchange v[i] and v[j] */
void my_swap(int v[], int i, int j)
{
   int temp;

   temp = v[i];
   v[i] = v[j];
   v[j] = temp;
}