代码

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

评测结果