Openjudge noi 2.1 1749: Digital Square

【 Topic link 】

OpenJudge NOI 2.1 1749: Number squares

【 Topic test site 】

1. enumeration

【 Their thinking 】

Solve equations by enumerating

• enumerable object ：$a_1,a_2,a_3$
• Enumeration range ：$0\le a_1,a_2,a_3\le n$
• Enumeration condition ：
  $(a_1+a_2)\%2=0$
  $(a_2+a_3)\%3=0$
  $(a_1+a_2+a_3)\%5=0$

Enumerate the qualified $a_1,a_2,a_3$, choice $a_1+a_2+a_3$ The largest group .

【 Solution code 】

#include<bits/stdc++.h>
using namespace std;
int main()
{
    
    int n, mx = 0;//mx:a1+a2+a3 The maximum of  
    cin >> n;
    for(int a1 = 0; a1 <= n; ++a1)
        for(int a2 = 0; a2 <= n; ++a2)
            for(int a3 = 0; a3 <= n; ++a3)
            {
    
                if((a1+a2)%2 == 0 && (a2+a3)%3 == 0 && (a1+a2+a3)%5 == 0)
                    mx = max(mx, a1+a2+a3);
            }
    cout << mx;
    return 0;
}