程序代码：

#include <stdio.h>
int LOC;
int recurbinary(int *a,int key,int low,int high){
    int mid,flag=1;
    mid=(low+high)/2;
    if(mid==low+1){
        if(a[low]==key){
            LOC=low;
            return 1;
        }
        flag=0;
    }
    if(mid+1==high){
        if(a[high]==key){
            LOC=high;
            return 1;
        }
        flag=0;
    }
    if(a[mid]==key){
        flag=0;
        LOC=mid;
        return 1;
    }
    if(recurbinary(a,key,low,mid) && flag)
        recurbinary(a,key,mid,high);
}
int main(){
    int a[]={1,8,6,4,2,3,7,5,9};
    recurbinary(a,3,0,8);
    printf("LOC=%d\n",LOC);
    return 0;
}