这可能是全站最长的题解😒

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

bool rn(int x){
    if(x % 4 == 0 and (x % 100 != 0 or x % 400 == 0)){
        return 1;
    } else {
        return 0;
    }
}

int _day(int x,int y){
    if(y == 1 or y == 3 or y == 5 or y == 7 or y == 8 or y == 10 or y == 12){
        return 31;
    } else if(y == 2){
        if(rn(x)){
            return 29;
        } else {
            return 28;
        }
    } else {
        return 30;
    }
}
string pps(int x,string s,int si){
    int tmp = x,intsi = 0;
    string bans = "";
    while(tmp){
        bans += char(tmp % 10 + '0');
        tmp /= 10;
        intsi ++;
    }
    string cans = "";
    for(int i = 0;i < si - intsi;i ++){
        cans += '0';
    }
    bans += cans;
    reverse(bans.begin(),bans.end());
    return s + bans;
}

string to_string(int x,int y,int z){
    string ans = "";
    ans = pps(x,ans,4);
    ans = pps(y,ans,2);
    ans = pps(z,ans,2);
    return ans;
}

string _plus(string s){
    string tmp = s;
    int i = s.size() - 1;
    int z = (s[i - 1] - '0') * 10 + s[i] - '0';
    i -= 2;
    int y = (s[i - 1] - '0') * 10 + s[i] - '0';
    i -= 2;
    int x = (s[i - 3] - '0') * 1000 + (s[i - 2] - '0') * 100 + (s[i - 1] - '0') * 10 + s[i] - '0';
    int day = _day(x,y);
    z ++;
    if(z > day){
        z = 1;
        y ++;
    }
    if(y > 12){
        y = 1;
        x ++;
    }
    string ans = to_string(x,y,z);
    return ans;
}

int main(){
    string a,b;
    cin >> a >> b;
    if(a == b){
        cout << 0;
        return 0;
    }
    int ans = 0;
    while(1){
        string tmp = a;
        reverse(tmp.begin(),tmp.end());
        if(tmp == a){
            ans ++;
        }
        a = _plus(a);
        if(a == b){
            break;
        }
    }
    cout << ans;
    return 0;
}