代码

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

评测结果