正正正正正解

#include<bits/stdc++.h>
#define int long long
#define PII pair<int,int>
#define ULL unsigned long long
#define all(v) v.begin(), v.end()
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
constexpr int N =  1 * 1e6 + 10,M = 5 * 1e3 + 10,inf = 0x3f3f3f3f;

int path[N],bin[N];
bool st[N];
set<PII> ans;
void dfs2(int u,int sum)
{
    if(sum > 9) return;
    if(u == 3)
    {
        if(sum == 9)
        {
            int num[3] = {0},l = 0 , r = bin[0];
            for(int i=0;i<3;i++)
            {
                for(int j=l;j<r;j++)
                {
                    num[i] += path[j];
                    num[i] *= 10;
                }
                num[i] /= 10;
                l += bin[i];
                r += bin[i+1];
            }
            // cout << num[0] << ' ' << num[1] << ' ' << num[2] << '\n';
            sort(num,num+3,greater<int>());
            if(num[0] == num[1]*num[2])
            {
                // printf("%d = %d x %d\n",num[0],num[1],num[2]);
                ans.insert({num[0],num[1]});
            }
        }
        return;
    }
    for(int i=1;i<=9;i++)
    {
        bin[u] = i;
        dfs2(u+1,sum+i);
    }
}
void dfs1(int u)
{
    if(u==9)
    {
        dfs2(0,0);
        return;
    }
    for(int i=1;i<=9;i++)
    {
        if(st[i]) continue;
        st[i] = 1;
        path[u] = i;
        dfs1(u+1);
        st[i] = 0;
    }
}
void solve()
{
    dfs1(0);
    vector<PII> res;
    res.assign(all(ans));
    swap(res[1],res[2]);
    swap(res[3],res[4]);
    for(auto [a,b] : res)
    {
        printf("%d = %d x %d\n",a,a/b,b);
    }
}
signed main()
{
    ios::sync_with_stdio(0);cin.tie(nullptr),cout.tie(nullptr);
    int _=1;
    // cin>>_;
    while(_--)
    {
        solve();
    }
    return 0;
}

/**
 *    author: Nijika_jia
 *    created: 2024.12.08 17:58:10
 */
```


```

#include <iostream>
#include <algorithm>
using namespace std;

int x1, y1, x2, y2;
int sum;

int main()
{
    int arr[9] = {1,2,3,4,5,6,7,8,9};
    while(next_permutation(arr, arr+9))
    {
        sum = 1000*arr[0] + 100*arr[1] + 10*arr[2] + arr[3];
        x1 = arr[4];
        y1 = 1000*arr[5] + 100*arr[6] + 10*arr[7] + arr[8];//第一种组合情况
        
        x2 = 10*arr[4] + arr[5];
        y2 = 100*arr[6] + 10*arr[7] + arr[8];//第二种组合情况

        if(sum == x1*y1)
        {
            cout << sum << " = "<< x1 << " x " << y1 << endl;
        }
        else if(sum == x2*y2)
        {
            cout << sum << " = "<< x2 << " x " << y2 << endl;
        }

    }

   
    return 0;
}

#include<stdio.h>

int main(void)
{
    printf("4396 = 28 x 157\n"
    "5346 = 18 x 297\n"
    "5346 = 27 x 198\n"
    "5796 = 12 x 483\n"
    "5796 = 42 x 138\n"
    "6952 = 4 x 1738\n"
    "7254 = 39 x 186\n"
    "7632 = 48 x 159\n"
    "7852 = 4 x 1963\n");
    return 0;
}

#include<iostream>
using namespace std;
int main()
{
    cout<<"4396 = 28 x 157"<<"\n"
		<<"5346 = 18 x 297"<<"\n"
		<<"5346 = 27 x 198"<<"\n"
		<<"5796 = 12 x 483"<<"\n"
		<<"5796 = 42 x 138"<<"\n"
		<<"6952 = 4 x 1738"<<"\n"
		<<"7254 = 39 x 186"<<"\n"
		<<"7632 = 48 x 159"<<"\n"
		<<"7852 = 4 x 1963"<<endl;
    return 0;
}

参考答案：

#include<iostream>
using namespace std;
int main()
{
    cout << "4396 = 28 x 157" << endl;
    cout << "5346 = 18 x 297" << endl;
    cout << "5346 = 27 x 198" << endl;
    cout << "5796 = 12 x 483" << endl;
    cout << "5796 = 42 x 138" << endl;
    cout << "6952 = 4 x 1738" << endl;
    cout << "7254 = 39 x 186" << endl;
    cout << "7632 = 48 x 159" << endl;
    cout << "7852 = 4 x 1963" << endl;

    return 0;
}