代码

int binary_search(const unsigned *a, int n, unsigned x)
{
	int l=0,r=n,ans=0;
	while(l<r)
	{
		int mid=(l+r)/2;
		if(a[mid]<x)l=mid+1;
		else r=mid,ans=mid;
	}
	return ans;
}

评测结果