糖果数量(交互)//Gym-101375H//二分

题目

Obs: this is an interactive problem. More information is under the “Interaction” section.

MaratonIME is gathering to start another group practice. This time, Renzo decided to reward the students with candies as they solve problems. Curious as they are, the members of MaratonIME started to guess how many candies did Renzo bring. For each question, Renzo answered if the amount of candies was higher, lower or equal to the number asked.

Breno, noticing that the amount of candies could be very high, decided to limit the number of queries to 50. This way, the practice would start as soon as possible.

Renzo bought at least 1 and no more than 109 candies. Find how many candies were bought by Renzo with no more than 50 questions.

Input
For every question asked, read a character. It will be " > " if the amount of Renzo’s candies is higher than your guess, " < " if the amount of Renzo’s candies is lower than your guess or " = " if your guess is equal to the amount of Renzo’s candies.

Output
You must print every query in the format “Q y”, where y is the number guessed, and 1 ≤ y ≤ 109. After printing a question, you need to flush the output. Check the “Interaction” section for examples of how to flush the output.

Interaction
To ask Renzo a question, print the query in the format above. After printing a question, you need to flush the output. See examples below for each language:

C: fflush(stdout)

C++: cout.flush()

Java: System.out.flush()

Python: sys.stdout.flush()

Pascal: flush(output)

After each query, read a character as described above.

As soon as Renzo answers your question with “=” the program has to terminate. Your answer will be considered correct if you asked no more than 50 questions.

Example
Input
>
<
=
Output
Q 1
Q 3
Q 2
Note
In the example, the number of candies is 2. The answer is considered to be correct because only 3 out of the 50 possible questions were asked to obtain the character " = ".

Make sure to flush the output after printing each question!
题意
告诉你大了还是小了,猜糖果数量。
链接:http://codeforces.com/gym/101375/problem/H

思路

二分询问

代码

#include <iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include <queue>
#include <cmath>
using namespace std;

int main()
{
    int high=1e9+1;
    int low=0;
    char ch;
    int temp;
    while(1){
        temp=(high+low)/2;
        cout<<"Q "<<temp<<endl;
        cout.flush();
        ch=getchar();
        getchar();
        if(ch=='>') low=temp;
        else if(ch=='<') high=temp;
        else if(ch=='=') break;
    }
    return 0;
}

注意

注意初值左闭右开