C++之日历

日历的元素
- 年月日
- 星期

如何加入星期元素？
提示：1900.1.1为星期一
以此类推，根据相差天数获得每个月第一天的星期数

#include <iostream>
using namespace std;
class Calendar {
    private:
        int year,month,day;
    public:
        Calendar() {
            year = month = day = 0;
        }
        bool leapYear(int y) {
            if ((y % 4 == 0 && y % 100 != 0) || y % 400 == 0) return true;
            else return false;
        }
        void setYear(int tmp) {
            year = tmp;
        }
        void setSomeDay(int x,int y,int z) {
            year = x;
            month = y;
            day = z;
        }
        int getDay(int m) {
            if (m==1 || m==3 || m==5 || m==7 || m==8 || m==10 || m==12) return 31;
            else if (m==4 || m==6 || m==9 || m==11) return 30;
            else {
                if (leapYear(year)) return 29;
                else return 28;
            }
        }
        //已知 1900.1.1 为星期一 
        int difYear() {
            int dif = year - 1900;
            int num = 0;
            for (int i = 0; i < dif; ++i) {
                if (leapYear(1900+i)) num += 366;
                else num += 365;
            }
            return num;
        }
        int difDay() {
            int dif = difYear();
            for (int i = 0; i < month; ++i) {
                dif += getDay(i);
            }
            dif += day;
            return dif;
        }
        void printDay() {
            int num = difDay()%7;
            switch (num) {
                case 1: cout << "Monday" << endl; break;
                case 2: cout << "Thesday" << endl; break;
                case 3: cout << "Wednesday" << endl; break;
                case 4: cout << "Thurday" << endl; break;
                case 5: cout << "Friday" << endl; break;
                case 6: cout << "Saturday" << endl; break;
                case 7: cout << "Sunday" << endl; break;
            }
        }
        void printYear() {
            int num = difYear();
            for (int i = 1; i <= 12; ++i) {
                cout << "Mon Tue Wed Thu Fri Sat Sun" << endl;
                switch (i) {
                    case 1: case 3: case 5: case 7: case 8: case 10: case 12:
                        for (int j = 0; j < num%7; ++j) cout << "    ";
                        for (int k = 1,m = num%7 + 1; k <= 31; ++k,++m) {
                            if (k < 10) cout << k << "   ";
                            else cout << k << "  ";
                            if (m % 7 == 0) cout << endl; 
                        }
                        cout << endl;
                        num += 31;
                        break;
                    case 4: case 6: case 9: case 11:
                        for (int j = 0; j < num%7; ++j) cout << "    ";
                        for (int k = 1,m = num%7 + 1; k <= 30; ++k,++m) {
                            if (k < 10) cout << k << "   ";
                            else cout << k << "  ";
                            if (m % 7 == 0) cout << endl;
                        }
                        cout << endl;
                        num += 30;
                        break;
                    case 2:
                        if (leapYear(year)) {
                            for (int j = 0; j < num%7; ++j) cout << "    ";
                            for (int k = 1,m = num%7 + 1; k <= 29; ++k,++m) {
                                if (k < 10) cout << k << "   ";
                                else cout << k << "  ";
                                if (m % 7 == 0) cout << endl;
                            }
                            cout << endl;
                            num += 29;
                        } else { 
                            for (int j = 0; j < num%7; ++j) cout << "    ";
                            for (int k = 1,m = num%7 + 1; k <= 28; ++k,++m) {
                                if (k < 10) cout << k << "   ";
                                else cout << k << "  ";
                                if (m % 7 == 0) cout << endl;
                            }
                            cout << endl;
                            num += 28;
                        }   
                }
            }
        }
};
int main () {
    Calendar test;  
    test.setYear(2017);
    test.printYear();
    test.setSomeDay(2017,11,27);
    test.printDay();
}

主要考虑距离多少天后如何得知第一天的星期数，用模运算即可