推断的距离1970年1一个月1天从日期数

#include <stdlib.h>

/******************************************************************
特征: 输入日期，计算距离19701月1日的天数

输入:
    年月日，输入年份范围【1970，2100】，输入年月日的有效性须要推断

输出:
     DaysSince1970：距离1970年1月1日的天数
     已知 1970年1月1日为星期四
     异常时，输出不须要关注

返回:
1 上班
0 休假
-1 表示异常

     依据国家规定：周一到周五须要上班。
     依据公司规则：月末周六须要上班。

     注：因为项目紧张，国家规定的节假日假设在周一到周五须要上班^_^。

举例：
    输入：Year = 1970, Month = 1, Day = 3 ，输出 2。返回值为 0 休假

********************************************************************/
#define IS_LEAP_YEAR(y) ((y) / 4 - (y) / 100 + (y) / 400 - (y - 1) / 4 + (y - 1) / 100 - (y - 1) / 400)

int DayNumber[][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}};
int dayofweek(int y, int m, int d) // 0  =  Sunday
{
    static int t[] = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};

    y -= m < 3;
    return (y + y / 4 - y / 100 + y / 400 + t[m - 1] + d) % 7;
}

int accumulationdayfrom1970(int *DaysSince1970, int Year, int Month, int Day)
{
    *DaysSince1970 = 0;

    for (int i = 1970; i < Year; i++)
    {
        if (IS_LEAP_YEAR(i))
        {
            *DaysSince1970 += 366;
        }
        else
        {
            *DaysSince1970 += 365;
        }
    }

    for (int i = 1; i < Month; i++)
    {
        int xs = IS_LEAP_YEAR(Year);
        *DaysSince1970 += DayNumber[IS_LEAP_YEAR(Year)][i];
    }

    *DaysSince1970 += Day - 1;
    return *DaysSince1970;
}

int GetCurrentDate(int *DaysSince1970, int Year, int Month, int Day)
{
    if (NULL == DaysSince1970)
    {
        return -1;
    }

    if ((Year < 1970) || (Year > 2100))
    {
        return -1;
    }

    if ((Month > 12) || (Month <= 0))
    {
        return -1;
    }

    int IsLeapYear = IS_LEAP_YEAR(Year); // 闰年返回1

    int weekday = dayofweek(Year, Month, Day);

    if ((Day > DayNumber[IsLeapYear][Month]) || (Day <= 0))
    {
        return -1;
    }

    *DaysSince1970 = accumulationdayfrom1970(DaysSince1970, Year, Month, Day);

    if ((0 < weekday) && (weekday < 6))
    {
        return 1;
    }
    else if (0 == weekday)
    {
        return 0;
    }

    if (weekday == 6)
    {
        if (IsLeapYear)
        {
            switch (Month)
            {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                if ((25 <= Day) && (Day <= 31))
                {
                    return 1;
                }
                else
                {
                    return 0;
                }

                break;
            case 4:
            case 6:
            case 9:
            case 11:
                if ((24 <= Day) && (Day <= 30))
                {
                    return 1;
                }
                else
                {
                    return 0;
                }

                break;
            case 2:
                if ((23 <= Day) && (Day <= 29))
                {
                    return 1;
                }
                else
                {
                    return 0;
                }

                break;
            default:
                ;
            }
        }
        else
        {
            switch (Month)
            {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                if ((25 <= Day) && (Day <= 31))
                {
                    return 1;
                }
                else
                {
                    return 0;
                }

                break;
            case 4:
            case 6:
            case 9:
            case 11:
                if ((24 <= Day) && (Day <= 30))
                {
                    return 1;
                }
                else
                {
                    return 0;
                }

                break;
            case 2:
                if ((22 <= Day) && (Day <= 28))
                {
                    return 1;
                }
                else
                {
                    return 0;
                }

                break;
            default:
                ;
            }
        }
    }

    return -1;
}

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