N days after the day of the week

#include <stdio.h> #include <stdlib.h>/*n days later is the day of the week */int monthdays[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, };typedef struct{int year;int month;int Day;} Date;date getnextday (date date1);D ate getnday (date date1, int n); int islastdayofmonth (int, int month, int day); int GE Tweekday (int, int month, int day), int isgoodyear (int), int isgoodmonth (int month), int isgoodday (int, int mon th, int day), int isleapyear (int), int dayofyear (int, int month, Int. day), int daysbetweenyear (int year1, int year2 int daysbetweendays (int year1, int month1, int day1, int year2, int month2, int day2); int main () {int year1, month1, Day1 , N;while (Fflush (stdin), scanf ("%d%d%d%d", &year1, &month1, &day1,&n)! = EOF) {if (Isgoodyear (YEAR1) && isgoodmonth (month1) && isgoodday (year1, Month1, day1)) {//To determine if the input is valid date date;date.year = year1; Date.month = Month1;date.day = Day1;date Date2 = Getnday (date,n);p rintf ("%d/%d/%d\n", date2.year,date2.month,dAte2.day);} elseprintf ("Please input a right date.\n");} System ("pause"); return 0;} int islastdayofmonth (int, int month, int day) {if (Isleapyear (year) && (month = = 2)) if (day = =) return 1;els Ereturn 0;else if (month = = 2) if (day = =) return 1;elsereturn 0;else if (month = = 4) | | (Month = = 6) | | (Month = = 9) | | (Month = = 11)) if (day = =) return 1;elsereturn 0;elseif (day = =) return 1;elsereturn 0;} Date Getnextday (date date1) {Date date2;if (!islastdayofmonth (Date1.year, Date1.month, Date1.day)) {date2.year = Date1.year;date2.month = Date1.month;date2.day = Date1.day + 1;} Else{date2.day = 1;if (Date1.month = =) {Date2.month = 1;date2.year = Date1.year + 1;} Else{date2.month = date1.month + 1;date2.year = date1.year;}} return date2;} Date Getnday (date date1, int n) {Date date2 = date1;for (int i = 0; i < n; ++i) {date2 = Getnextday (date2);} return date2;} int Getweekday (int year, int month, Int. day) {//Datum take 2016/1/3, Sunday//sun return 0//mon-sat respectively return 1-6if ((year >=) && (Mo NtH >= 1) && (Day >= 3)) return Daysbetweendays (1, 3, year, month, day)% 7;elsereturn (7-daysbetweenda YS (year, month, Day, 2016, 1, 3)% 7)% 7;} int daysbetweendays (int year1, int month1, int day1, int year2, int month2, int day2) {//date 1< date Two is negative//date 1> date two is positive int da Ys1 = DayOfYear (year1, Month1, day1); int days2 = DayOfYear (year2, Month2, day2); int days3 = Daysbetweenyear (year1, year2); int totaldays = days2 + Days3-days1;return totaldays;} int daysbetweenyear (int year1, int year2) {//year1 < year2 is positive//year1 > year2 is negative int maxyear = (year1 > year2)? yea R1:year2;int minyear = (year1 > Year2)?  Year2:year1;int totaldays = 0;for (int i = minyear; i < maxyear; ++i) if (Isleapyear (i)) totaldays + = 366;elsetotaldays + = 365;if (minyear = = year1) return totaldays;elsereturn-totaldays; int dayofyear (int, int, month, int day) {//The first days of the year int total = 0;for (int i = 0; i < month-1; ++i) Total + = monthdays[ I];total + = Day;if (Isleapyear (year) && (month > 2) total++;return total;} int isleapyear (int year) {if ((year% 4 = = 0) && (year% 100! = 0)) | | (Year% 400 = = 0)) return 1;elsereturn 0;} int isgoodyear (int year) {if (year >= 1900) return 1;elsereturn 0;} int isgoodmonth (int month) {if ((month >= 1) && (month <=)) return 1;elsereturn 0;} int Isgoodday (int year, Int. month, int day) {switch (month) {Case 2:if (isleapyear (year)) if (day >= 1) && lt;=) return 1;else if ((Day >= 1) && (day <=)) return 1;elsereturn 0;case 4:case 6:case 9:case 11:if ( (Day >= 1) && (day <=)) return 1;elsereturn 0;case 1:case 3:case 5:case 7:case 8:case 10:case 12:if ( >= 1) && (day <=)) return to 1;elsereturn 0;default:printf ("Month error in day judge.\n"); return 0;}}

　　

N days after the day of the week