题解 | 等式填充问题

#include<bits/stdc++.h>
using namespace std;

int gcd(int x, int y){
    while(y != 0){
        int temp = y;
        y = x % y;
        x = temp;
    }
    return x;
}

bool judge(int x, int y){
    if(y == 1){
        return false;
    }
    return gcd(x, y) == 1;
}

int main(){
    int a[9] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
    do{
        int p = a[0] * 10 + a[1];
        int q = a[3] * 10 + a[4];
        int r = a[6] * 10 + a[7];
        int x = a[2];
        int y = a[5];
        int z = a[8];
        if(judge(p, x) && judge(q, y) && judge(r, z)){
            if((p * y + q * x) * z == r * x * y){
                cout << p << "/" << x << "+" << q << "/" << y << "=" << r << "/" << z << endl;
            }
        }
    }while(next_permutation(a, a + 9));
    return 0;
}

完全不知道next_permutation这个东西