BAEKJOON 1072 - 게임

문제: https://www.acmicpc.net/problem/1072

앞선 문제들과 같이 이진 탐색으로 쉽게 풀 수 있는 문제입니다. 

#pragma warning (disable:4996)
#include <cstdio>
#include <cstring>
#include <climits>
#include <algorithm>
 
using namespace std;
typedef long long ll;
 
bool isChanged(int x, int y, ll mid)
{
    ll oldValue = (ll)y * 100 / x;
    ll newValue = (mid + (ll)y) * 100 / (x + mid);
    return newValue != oldValue;
}
 
int binarySearch(int x, int y)
{
    ll low, high, ret;
    low = 0;
    high = ret = x;
    while (low <= high)
    {
        ll mid = (low + high) / 2;
        if (!isChanged(x, y, mid))
        {
            low = mid + 1;
        }
        else
        {
            ret = min(ret, mid);
            high = mid - 1;
        }
    }
    return ret;
}
 
int main()
{
    int x, y;
    while (scanf("%d %d", &x, &y) != EOF)
    {
        if ((ll)y * 100 / x >= 99LL)
            printf("-1\n");
        else
            printf("%d\n", binarySearch(x, y));
    }    
    return 0;
}