代码

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

评测结果