代码

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

评测结果