c语言简单日历代码

#include <iostream>
using namespace std;
void fun2(int firstday, int flag);//输出日历
int fun1(int year,int *flag);//计算所输年份的第一天为星期几并且判断是否为闰年(闰年返回0，非闰年返回1)
int main()
{
	int year,firstday,flag;
	cout << "输入年份：";
	cin >> year;
	firstday = fun1(year, &flag);
	fun2(firstday, flag);
}
int fun1(int year,int *flag)
{
	int sum = 0;
	for (int i = 1; i < year; i++)//计算有多少闰年
	{
		if (i % 400 == 0 || i % 4 == 0 && i % 100 != 0)
		{
			sum++;
		}
	}
	if (year % 400 == 0 || year % 4 == 0 && year % 100 != 0)//判断这年是否为闰年
	{
		*flag = 0;
	}
	else
		*flag = 1;
	return ((year - sum) * 365 + sum * 366) % 7;
}
void fun2(int firstday, int flag)
{
	int sum = 0;//在每个月里记天数
	for (int a = 1; a <= 12; a++)
	{
		cout << "           " << a << "月" << endl;//输出月份
		cout << "--------------------------" << endl;
		cout << "一  二  三  四  五  六  日" << endl;//输出星期
		if (firstday == 0)//第一天为星期日前面应空多少格
		{
			for (int i = 1; i < 7; i++)
				cout << "    ";
		}
		else for (int i = 1; i < firstday; i++)//第一天不为星期日前面应空多少格
		{
			cout << "    ";
		}
		if (a == 1 || a == 3 || a == 5 || a == 7 || a == 8 || a == 10 || a == 12)//输出大月
		{
			for (int j = 1; j <= 31; j++)
			{
				printf("%-4d", j);
				sum++;
				if ((sum + firstday-1) % 7 == 0)
					cout << endl;
			}
		}
		else if (a == 4 || a == 6 || a == 9 || a == 11)//输出小月
		{
			for (int j = 1; j <= 30; j++)
			{
				printf("%-4d", j);
				sum++;
				if ((sum + firstday-1) % 7 == 0)
					cout << endl;
			}
		}
		else if (a == 2)//输出二月
		{
			if(flag==1)//非闰年
				for (int j = 1; j <= 28; j++)
				{
					printf("%-4d", j);
					sum++;
					if ((sum + firstday-1)%7 == 0)
						cout << endl;
				}
			else//闰年
				for (int j = 1; j <= 29; j++)
				{
					printf("%-4d", j);
					sum++;
					if ((sum + firstday-1) % 7 == 0)
						cout << endl;
				}
		}
		firstday = (sum % 7 + firstday)%7;//判断下一个月的一号是星期几
		sum = 0;
		cout << endl;
	}
}