题目链接

这是爆掉的C++(long long 爆了)

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;

long long reverse(long long n) {
    long long rev = 0;
    while (n > 0) {
        int digit = n % 10;
        rev = rev * 10 + digit;
        n /= 10;
    }
    return rev;
}

bool isPalindrome(long long n) {
    long long rev = reverse(n);
    return n == rev;
}

int main() {
    int T;
    cin >> T;
    while (T--) {
        long long n;
        int k;
        cin >> n >> k;
        bool found = false;
        int steps = 0;
        for (int i = 0; i < k; i++) {
            long long nx = reverse(n);
            long long temp = n + nx;
            if (isPalindrome(temp)) {
                n = temp;
                steps = i + 1;
                found = true;
                break;
            }
            n = temp;
        }
        if (found) {
            cout << n << " " << steps << endl;
        }
        else {
            cout << n << " " << -1 << endl;
        }
    }
    return 0;
}

博主很懒，所以干脆换成了Java

import java.math.BigInteger;
import java.util.Scanner;

public class Main {

    public static BigInteger reverse(BigInteger n) {
        String str = n.toString();
        StringBuilder sb = new StringBuilder();
        for (int i = str.length() - 1; i >= 0; i--) {
            sb.append(str.charAt(i));
        }
        int st = 0;
        while (st < sb.length() - 1 && sb.charAt(st) == '0') {
            st++;
        }
        return new BigInteger(sb.substring(st));
    }

    public static boolean isPalindrome(BigInteger n) {
        String str = n.toString();
        int l = 0;
        int r = str.length() - 1;
        while (l < r) {
            if (str.charAt(l) != str.charAt(r)) {
                return false;
            }
            l++;
            r--;
        }
        return true;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int T = scanner.nextInt();

        for (int t = 0; t < T; t++) {
            BigInteger n = scanner.nextBigInteger();
            int k = scanner.nextInt();
            boolean found = false;
            int steps = 0;
            if (isPalindrome(n)) {
                System.out.println(n + " 0");
                continue;
            }
            for (int i = 0; i < k; i++) {
                BigInteger reversed = reverse(n);
                n = n.add(reversed);
                steps = i + 1;
                if (isPalindrome(n)) {
                    found = true;
                    break;
                }
            }
            if (found) {
                System.out.println(n + " " + steps);
            } else {
                System.out.println(n + " -1");
            }
        }

    }
}