代码

int binary_search(const unsigned *a, int n, unsigned x)
{
	int l=0,r=n,mid;
        while(l<=r){
                mid=l+r>>1;
                if(a[mid]==x) return mid;
                else if(a[mid]<x) l=mid+1;
                else if(a[mid]>x) r=mid-1;
        }
        return 0;
}

评测结果