随机化快速排序代码

 当年抓破头皮没想出来，溜了一眼算法导论豁然开朗。其实就是排以前交换一下pivot。

 

#include <stdlib.h> 
#include <time.h>
#include <stdio.h>

typedef int Record; 

void QuickSort (Record r[],int s,int t);

void QuickSort (Record r[],int s,int t)
...{
        int low=s;
        int high=t;

        Record pivot;
        ...{
                int t,tn; 
                srand(time(NULL));
                tn=rand()%(high-low+1)+low;
                t=r[low];
                r[low]=r[tn];
                r[tn]=t; 
        }
         
        pivot=r[s];
        while (low<high)...{
                while (low<high && r[high]>pivot)
                        high--;
                if (low<high) r[low++]=r[high];
                while (low<high && r[low]<pivot)
                        low++;
                if (low<high) r[high--]=r[low];
        }
        r[low]=pivot;
        if (s<low) QuickSort(r,s,low-1);
        if (t>high) QuickSort(r,high+1,t);
}