輸入年份和月份打印當月日歷

/*
    QQ：778138708
    date:2020-5-14
    輸入年份和月份，打印當月日歷
 
*/
/*
    日期轉換為星期的方法
    W= (d+2*m+3*(m+1)/5+y+y/4-y/100+y/400+1)%7
    在公式中d表示日期中的日數，m表示月份數，y表示年數
    把一月和二月看成是上一年的十三月和十四月，例：如果是2004-1-10則換算成：2003-13-10來代入公式計算。
*/
#include <stdio.h>
int weekNum(int year, int month, int day);
int isLeap(int year);
void printBlank(int n);
int main(void)
{
    int year, month;
    int leap, days;
    int i, firstDateWeek, dateWeek;
    int tab[2][13] = {{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
        {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}};
    
    printf("請輸入一個年份(例如:2020):");
    scanf("%d", &year);
    printf("請輸入一個月份(1-12的數字):");
    scanf("%d", &month);
    
    leap = isLeap(year);
    days = tab[leap][month];    //每個月的總天數
    
    printf("\t\t%d年%d月\n", year, month);
    printf("--------------------------\n");
    printf("日\t一\t二\t三\t四\t五\t六\n");
    
    //計算1號的星期數
    firstDateWeek = weekNum(year, month, 1);
    printBlank(firstDateWeek);      //每個月日歷前的空白
    
    //開始打印日期
    for (i = 1; i <= days; i++) {
        printf("%d\t", i);
        dateWeek = weekNum(year, month, i);
        if (dateWeek == 6) {
            printf("\n");
        }
    }
    
    printf("\n");
    
    return 0;
}
//日期轉換為星期
int weekNum(int year, int month, int day)
{
    int week;
    
    if (month == 1 || month == 2) {
        year =year - 1;
        month = 12 + month;
    }
    week = (day + 2 * month + 3 * (month + 1) / 5 + year + year / 4 - year / 100 + year / 400 + 1) % 7;
    
    return week;
}
//判斷閏年
int isLeap(int year)
{
    int leap = (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
    
    return leap;
}
//打印1號之前的空白
void printBlank(int n)
{
    int i;
    
    for (i = 0; i < n; i++)
    {
        printf("\t");
    }
}

 

方法二

#include <stdio.h>
#include <stdbool.h>

#define START_DAY_FOR_JAN_1_1800 3

void printMonth(int year, int month);
void printMonthTitle(int year, int month);
void printMonthBody(int year, int month);
int getStartDay(int year, int month);
int getTotalNumberOfDays(int year, int month);
int getNumberOfDaysInMonth(int year, int month);
bool isLeapYear(int year);
int main(void)
{
    int year, month;

    printf("請輸入一個年份:(例如:2020):");
    scanf("%d", &year);

    printf("請輸入一個月份:(1-12的數字):");
    scanf("%d", &month);

    printMonth(year, month);

    return 0;
}

//打印相應年份和月份的日歷
void printMonth(int year, int month)
{
    //打印日歷的開頭
    printMonthTitle(year, month);

    //打印日歷內容
    printMonthBody(year, month);
}

//打印日歷的開頭
void printMonthTitle(int year, int month)
{
    printf("\t\t%d年%d月\n",year,month);
    printf("--------------------------\n");
    printf("日\t一\t二\t三\t四\t五\t六\n");

}

//打印日歷的內容
void printMonthBody(int year, int month)
{
    int startDay = getStartDay(year, month);
    int i;

    //在當月的第一天前面加上若干個空格
    for (i = 0; i < startDay; i++)
    {
        printf("\t");
    }
    
    for (i = 1; i <= getNumberOfDaysInMonth(year, month); i++)
    {
        printf("%2d\t", i);
        //星期六換行
        if ((i + startDay) % 7 == 0)
        {
            printf("\n");
        }
    }
    printf("\n");
}

//返回某月第一天是星期幾
int getStartDay(int year, int month)
{
    return (START_DAY_FOR_JAN_1_1800 + getTotalNumberOfDays(year, month)) % 7;

}
//返回從1800年1月1日至year年month月1日之間的天數
int getTotalNumberOfDays(int year, int month)
{
    int totalDays = 0;
    int i;
    for (i = 1800; i < year; i++)
    {
        //閏年問題
        if (isLeapYear(i))
        {
            totalDays += 366;
        }
        else
        {
            totalDays += 365;
        }
    }
    
    for (i = 1; i < month; i++)
    {
        totalDays += getNumberOfDaysInMonth(year, i);
    }

    return totalDays;
}
//返回每個月的天數
int getNumberOfDaysInMonth(int year, int month)
{
    int days;

    if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12)
    {
        days = 31;
    }
    else if (month == 4 || month == 6 || month == 9 || month == 11)
    {
        days = 30;
    }
    else if (month == 2)
    {
        //閏年問題
        days = isLeapYear(year)?29:28;
    }
    else
    {
        days = 0;
    }

    return days;
}

//判斷是否是閏年
bool isLeapYear(int year)
{
    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}