線性快速劃分尋找第一個順序統計量

#include <stdio.h>#include <conio.h>int partition(int *R,int low,int high)                          //快速劃分{    int key;    key=R[low];    while(low<high)    {        while(low<high&&R[high]>key)    high--;        if(low<high)        {            R[low]=R[high];            low++;        }        while(low<high&&R[low]<key)     low++;        if(low<high)        {            R[high]=R[low];            high--;        }        R[low]=key;    }    return low;}int SELECT(int *A,int p,int r,int i)                             //選擇{    int k;    int q;    if(p==r)        return A[p];    q=partition(A,p,r);    k=q-p+1;    if(k==i)        return A[q];    else if(i<k)        return SELECT(A,p,q-1,i);    else        return SELECT(A,q+1,r,i-k);}int main(){    int i;    int key;    int a[20]={21,43,44,2,8,9,3,12,35,7,11,32,33,99,55,13,26,34,15,24};    printf("input the num of the order statistic:");    scanf("%d",&i);    key=SELECT(a,0,19,i);    printf("the ith order statistic is %d",key);    getch();    return 0;}