编辑代码

#include <stdio.h>


int halfFind(int a[],int length,int num){
    int low,high,mid,retIndex;
    low=0;  
    high=length-1;
    retIndex=-1;
    while(low<=high){
        mid=(low+high)/2;
        if(a[mid]==num){
            retIndex=mid;
            break;
        }else if(a[mid]>num){
            high=mid-1;
        }else{
            low=mid+1;
        }
    }
    return retIndex;
}

int main () {
    int a[]={1,3,5,7,9,11};
    int num=9;
    printf("所查找的元素在数组中的位置为：%d",halfFind(a,6,num));
    return 0;
}