这一天是星期几（难度：1颗星）

朴灿烈づ我的快乐病毒、 2022-06-15 07:50 233阅读 0赞

问题描述：

输入1个日期，日期的格式由3个正整数组成（正整数之间用空格分开），输出这一天是星期几，如果日期不合法，比如：2008 1 32（这个就不合法，因为天数超过了1月的最大天数31），直接输出“输入日期无效”，否则输出这一天是星期几。

输入举例：

2017 1 1

输出结果：  
星期天

参考代码：

#include <stdio.h>
    
    int arr[] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
    char szDays[7][5] = {
       "天", "一", "二", "三", "四", "五", "六"};
    
    int IsLeapYear(int year)
    {
        return ((year % 4 == 0) && (year % 100)) || (year % 400 == 0);
    }
    
    int GetPassedMonthDays(int year, int month, int day)
    {
       //计算因为月份相差的天数
        int sum = day;
        for (int i = 1; i < month; i++)
            sum += arr[i];
    
        if (month > 2 && IsLeapYear(year))
            sum += 1;
        return sum;
    }
    
    int GetDiffYearDays(int year1, int year2)
    {
       //计算因为年份，相差的天数
        int sum = (year2 - year1) * 365;
        for (int i = year1; i < year2; i++)
        {
            if (IsLeapYear(i))
                sum += 1;
        }
        return sum;
    }
    
    int isvalid(int year, int month, int day)
    {
       //判断输入的日期是否有效
        if (month < 0 || month > 12)
            return 0;
    
        if (day < 0)
            return 0;
    
        if (month == 2)
        {
            if ((IsLeapYear(year) && day > 29) || (!IsLeapYear(year) && day > 28))
                return 0;
        }
        else
        {
            if (day > arr[month])
                return 0;
        }
    
        return 1;
    }
    
    int IsGreater(int year1, int month1, int day1, int year2, int month2, int day2)
    {
       //判断两个日期那个更大
        if (year1 != year2)
            return year1 > year2 ? 1 : 0;
    
        if (month1 != month2)
            return month1 > month2 ? 1 : 0;
    
        if (day1 != day2)
            return day1 > day2 ? 1 : 0;
    
        return 0;
    }
    
    int main()
    {
        int year1, month1, day1, dayOfWeek1, nDayDiff;
        int year2 = 2017, month2 = 5, day2 = 27, dayOfWeek2 = 6;//以今天的时间为基准，2017-5-27，星期6
        printf("请输入日期的年月日,用空格隔开\n");
        scanf_s("%d%d%d", &year1, &month1, &day1);
        if (!isvalid(year1, month1, day1))
        {
            printf("输入日期无效\n");
            return 0;
        }
    
        if (IsGreater(year1, month1, day1, year2, month2, day2))
        {
            nDayDiff = GetDiffYearDays(year2, year1) - GetPassedMonthDays(year2, month2, day2) + GetPassedMonthDays(year1, month1, day1);
            dayOfWeek1 = (dayOfWeek2 + nDayDiff) % 7;
        }
        else
        {
            nDayDiff = GetDiffYearDays(year1, year2) - GetPassedMonthDays(year1, month1, day1) + GetPassedMonthDays(year2, month2, day2);
            dayOfWeek1 = ((dayOfWeek2 - nDayDiff) % 7 + 7) % 7;
        }
    
        printf("星期%s\n", szDays[dayOfWeek1]);
    
        return 0;
    }

运行结果：

![这里写图片描述][SouthEast]

[SouthEast]: /images/20220615/ac6e17bdec984e4684439d4d6c50559c.png