C++ 代码

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

int arr[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
int n;

bool is_prime(int y){
    if(y % 4 == 0 && y % 100 != 0 || y % 400 == 0) return true;
    else return false;
}

int limit(int y, int m){
    int leap = 0;
    if(is_prime(y)){
        leap = 1;
    }
    return m == 2 ? arr[m] + leap : arr[m];
}

//判断是不是合法的日期 
bool check(int d){
    int y = d / 10000;
    int m = d / 100 % 100;
    int d1 = d % 100;
    if(m < 1 || m > 12 || d1 < 1 || d1 > limit(y,m)) return false;
    else return true; 
}

int main(){
    cin >> n;
    for(int i = n / 10000; i < 10000; i++){
        int date = i;
        int x = i;
        while(x){
            date = date * 10 + x % 10;
            x /= 10;
        }
        if(date == n) continue;//得出的结果是同一天
        if(check(date)){
            cout << date << endl;
            break;
        }
    }
    for(int i = n / 10000; i < 10000; i++){
        int date = i;
        int x = i;
        while(x){
            date = date * 10 + x % 10;
            x /= 10;
        }
        if(date == n) continue;
        int AB = date / 10000 % 100, BA = date / 100 % 100;
        if(AB == BA) continue;
        if(check(date) && date / 1000000 == AB && date % 100 == BA){
            cout << date << endl;
            break;
        }
    }
    return 0;
}