用rand还有40分
二分怎么只有20分？

#include<iostream>
using namespace std;
int n = 500000000;
int m;
int main()
{
	int l = 1 , r = 1000000000;
	while(l <= r)
	{
		cout << n << endl;
		cin >> m;
		n = (l + r) >> 1;
		if(m == 0)
		{
			break;
		}
		else if(m == -1)
		{
			l = n + 1;
		}
		else if(m == 1)
		{
			r = n - 1;
		}
	}
	return 0;
}