代码

int binary_search(const unsigned *a, int n, unsigned x){
	unsigned l=0, r=n;
	while(l<r-255){
		unsigned mid=(l+r)>>1;
		if(a[mid]<x){
			l=mid+1;
		}
		else{
			r=mid;
		}
	}
	for(; a[l]^x; l++);
	return l;
}

评测结果