实现日历功能，输入年份月份，输出日历

#include<stdio.h>

int leap_year(int year)
{
	if(year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
	{
		return 1;
	}else
	{
		return 0;
	}
}

int determine_year_month_day(int *day,int month,int year)
{
	if(month != 2)
	{
		return day[month - 1];
	}else
	{
		return 28 + leap_year(year);
	}
}

int date_of_1900(int month,int year,int *day)
{
	int i,j;
	int sum = 0;
	for(i = 1900;i < year;++i)
	{
		if(leap_year(i) == 1)
		{
			sum += 366;
		}else if(leap_year(i) == 0)
		{
			sum += 365;
		}
	}

	for(j = 1;j < month;++j)
	{
		sum += determine_year_month_day(day,j,i);
	}
	return sum;
}

int printf_calendar(int month,int year,int *day)
{
	int i,j,max;
	max = determine_year_month_day(day,month,year);
	printf("       %d月      %d年       \n",month,year);
	printf("  一  二  三  四  五  六  日\n");
	int min = date_of_1900(month,year,day) % 7;
	for(j = min;j > 0;--j)
	{
		printf("    ");
	}

	for(i = 1;i <= max;++i)
	{
		printf("%4d",i);
		if((i+min) % 7 == 0)
		{
			putchar('\n');
		}
	}
}

int main(void)
{
	int year,month;
	int day[] = {31,28,31,30,31,30,31,31,30,31,30,31};
	printf("Please enter the year and month you want to query:");
	scanf("%d %d",&year,&month);
	if(month > 12 || month < 1)
	{
		printf("Input Error!\n");
	}
	printf_calendar(month,year,day);
	putchar('\n');
	return 0;
}

实现的结果如图所示：