用1、2、3、4、5、6、7、8、9这9 个数字填入等式使等式成立

直接暴力：

#include <iostream>
#include <algorithm>

using namespace std;

int Fun(int * a, int n) {
    int ans = 0;
    for (int i = 0; i < n; i++)
        ans = ans * 10 + a[i];
    return ans;
}

int main()
{
    int arr[9] = { 1,2,3,4,5,6,7,8,9 };
    int a = 0, b = 0, c = 0;
    do {
        a = Fun(arr, 2);
        b = Fun(arr + 2, 3);
        c = Fun(arr + 5, 4);
        if (c == a * b)
            cout << a << " * " << b << " = " << c << endl;
    } while (next_permutation(arr,arr + 9));
    return 0;
}

 2021-04-30