在 C 中创建日期计算器

Question

我需要用 C 创建一个基本的日期计算器，让用户以 YYYY-MM-DD 格式输入日期。我有它的基础知识。虽然我不需要，但我想多花点时间考虑闰年。程序运行良好；但是，它不能正确计算闰年。当我输入日期 2016-02-26 时，我应该得到 2016-03-04 的预期结果，但我得到的结果是 2016-03 -03。我认为如果我使用 if else 语句来实现以下使用模数的效果。

if (month == 2 && year % 4) days = 29; 
   else days = 28;

这是我的完整代码...

//Does not require <stdlib.h>
#include <stdio.h>

// Set variables
int newDay, newMonth, newYear, daysInMonth, daysRemain;
// Set structure for day month year
struct date {
    int day, month, year;
};
// set structure for date
struct date d1;

int main (void) {
    //Intro
    printf("Date calculation program by Keith A. Russell");
    //Asks for user input
    printf("\n\nPlease enter the year in four digit format (YYYY) ");
    scanf("%i", &d1.year);
    printf("\nEnter the month in two digit format (MM) ");
    scanf("%i", &d1.month);
    printf("\nEnter the day in two digit format (DD) ");
    scanf("%i", &d1.day);
    //Runs calculations to increase the date by a week
    newDay = d1.day + 7;
    newMonth = d1.month;
    newYear = d1.year;
    daysRemain = 0;
    //For if the next week is going to be greater than the next month
    if (newDay > 28)
        checkMonth();  //Runs checkMonth Function
    //Prints the dates
    printf("\nThe new date is %i-%i-%i: \n", newYear, newMonth, newDay);
}

checkMonth() {
    if (d1.month == 1 || 3 || 5 || 7 || 8 || 10 || 12)
        daysInMonth = 31;               //For months with 31 days
    if (d1.month == 2 && d1.year % 4)   //Attempt to calculate leap year
        daysInMonth = 29;
    else {
        daysInMonth = 28;           //All other years
    }
    if (d1.month == 4 || 6 || 9 || 11)  //For months with 30 days
        daysInMonth = 30;
    //Sets up to advance the year if approaching the end of year
    if (newDay > daysInMonth) {
        daysRemain = newDay - daysInMonth;
        newDay = daysRemain;
        newMonth++;
        checkYear();
    }
}
//Runs function to advance to the next year
checkYear() {
    if (d1.month == 12)
        if (daysRemain > 0) {
            newYear++;
            newMonth = 1;
        }
}

如果有更优雅的方法来计算闰年并将其包含在该程序中，我将不胜感激。谢谢。

Answer 1

首先这是错误的

if (d1.month == 1 || 3 || 5 || 7 || 8 || 10 || 12)

它永远是真的。你需要

if (d1.month == 1 || d1.month == 3 || d1.month == 5 ....)