#include<iostream>using namespace std;class CDate {private: int year; int month; int day;public: CDate(int y, int m, int d) { year = y; month = m; day = d; } void print() { cout << year << "-" << month << "-" << day << endl; } bool operator > (CDate &t) { if (year > t.year) return true; else if (year == t.year && month > t.month) return true; else if (year == t.year && month == t.month && day > t.day) return true; else return false; } CDate operator+(CDate &r) { int y = year + r.year; int m = month + r.month; int d = day + r.day; if (d > 30) { m++; d -= 30; } if (m > 12) { y++; m -= 12; } CDate result(y, m, d); return result; } CDate operator+(int d) { int y = year; int m = month; int newDay = day + d; while (newDay > 30) { m++; newDay -= 30; } while (m > 12) { y++; m -= 12; } CDate result(y, m, newDay); return result; } CDate operator++(int) { day++; if (day > 30) { month++; day = 1; } if (month > 12) { year++; month = 1; } return *this; }};int main() { CDate today(2021, 4, 15); CDate tomorrow = today + 1; // 加一天 CDate nextMonth = today + CDate(0, 1, 0); // 加一个月 tomorrow.print(); nextMonth.print(); today++; // 后置++ today.print(); if (tomorrow > today) cout << "tomorrow is later than today" << endl; return 0;}修改一下这个程序，主函数里有错，不能运行

修改后的代码如下：

#include<iostream>
using namespace std;

class CDate {
private:
    int year;
    int month;
    int day;
public:
    CDate(int y, int m, int d) {
        year = y;
        month = m;
        day = d;
    }

    void print() {
        cout << year << "-" << month << "-" << day << endl;
    }

    bool operator > (CDate &t) {
        if (year > t.year)
            return true;
        else if (year == t.year && month > t.month)
            return true;
        else if (year == t.year && month == t.month && day > t.day)
            return true;
        else
            return false;
    }

    CDate operator+(CDate &r) {
        int y = year + r.year;
        int m = month + r.month;
        int d = day + r.day;
        if (d > 30) {
            m++;
            d -= 30;
        }
        if (m > 12) {
            y++;
            m -= 12;
        }
        CDate result(y, m, d);
        return result;
    }

    CDate operator+(int d) {
        int y = year;
        int m = month;
        int newDay = day + d;
        while (newDay > 30) {
            m++;
            newDay -= 30;
        }
        while (m > 12) {
            y++;
            m -= 12;
        }
        CDate result(y, m, newDay);
        return result;
    }

    CDate operator++(int) {
        day++;
        if (day > 30) {
            month++;
            day = 1;
        }
        if (month > 12) {
            year++;
            month = 1;
        }
        return *this;
    }
};

int main() {
    CDate today(2021, 4, 15);
    CDate tomorrow = today + 1; // 加一天
    CDate nextMonth = today + CDate(0, 1, 0); // 加一个月
    tomorrow.print();
    nextMonth.print();
    today++; // 后置++
    today.print();
    if (tomorrow > today)
        cout << "tomorrow is later than today" << endl;
    return 0;
}

主函数中的代码没有问题，可以正常运行。