题目：1、编写函数，内容：输入年份判断是否为闰年，返回真假值。2、编写函数：输入年月，返回这一月的天数。3、输入日，返回是这一年的第几天。（注意：判断输入年月是否有效）
闰年是能被4整除不能被100整除且能被400整除的年份。闰年2月有29天，非闰年有28天。
#include<stdio.h>bool LeapYear(int year){return (year % 4 == 0 && year % 100 != 0 || year % 400 == 0);}int Month(int year,int month){int Day[13] = {29,31,28,31,30,31,30,31,31,30,31,30,31 }; //查表if (2 == month && LeapYear(year)){month = 0;}return Day[month];}int Get_Daynum(int year, int month, int day){int sum = 0;for (int i = 1; i < month; i++){sum += Month(year, i);}sum += day;return sum;}int main(){int year, month, day;char ch = 0;do{printf("请输入年份：");scanf("%d", &year);printf("请输入月份：");scanf("%d", &month);printf("请输入日：");scanf("%d", &day);LeapYear(year);Month(year, month);Get_Daynum(year, month, day);if (year < 1){printf("输入年份有误！\n");}if (month > 12 || month < 1){printf("输入月份有误！\n");}if (day < 1 || day > Month(year,month)){printf("输入天数有误！\n");}printf("是否继续（y/n）？：");rewind(stdin);scanf("%c",&ch);} while (ch == 'y' || ch == 'Y');printf("%d年%d月有%d天\n这一天是这一年的第%d天。\n", year, month, Month(year, month), Get_Daynum(year, month, day));}
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