也很简单

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

int main() {
    for(int i=1000;i<10000;i++){
		int t=i%10*1000+i/10%10*100+i/100%10*10+i/1000;
		if(i*9==t){
			cout<<i<<endl;
		}
	}
    return 0;
}

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

int main() {
    for(int i=1000;i<10000;i++){
		int t=i%10*1000+i/10%10*100+i/100%10*10+i/1000;
		if(i*9==t){
			cout<<i<<endl;
		}
	}
    return 0;
}

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

int reverse_number(int x) {
    int rev = 0;
    while (x > 0) {
        rev = rev * 10 + x % 10;
        x /= 10;
    }
    return rev;
}

int main() {
    for (int N = 1000; N <= 9999; ++N) {
        int rev_N = reverse_number(N);
        if (9 * N == rev_N) {
            cout << N << endl;
        }
    }
    return 0;
}