参考题解有个小甲鱼的，使用了结构体

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

struct Day {
    int year;
    int mon;
    int date;
} day1, day2;

void Date(int input, Day &day) {
    day.year = input / 10000;         // 提取年份
    day.mon = (input / 100) % 100;    // 提取月份
    day.date = input % 100;           // 提取日期
}

bool LeapYear(int year) {
    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}

int daysMonth(int year, int month) {
    int days[] = {31, 28, 31, 30, 31, 30 ,31, 31, 30, 31, 30, 31};
    if (month == 2 && LeapYear(year)) {
        return 29;
    }
    return days[month - 1];
}

int calculate(Day &day1, Day &day2) {
    int cnt = 1;   //应题目要求cnt初始为1
    while (!(day1.year == day2.year && day1.mon == day2.mon && day1.date == day2.date)) {
        day1.date++;
        if (day1.date > daysMonth(day1.year, day1.mon)) {
            day1.date = 1;
            day1.mon++;
  ...