89 lines
2.3 KiB
C
89 lines
2.3 KiB
C
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#include <stdio.h>
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#include "utils.h"
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/*
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You are given the following information, but you may prefer to do some research for yourself.
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1 Jan 1900 was a Monday.
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Thirty days has September,
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April, June and November.
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All the rest have thirty-one,
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Saving February alone,
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Which has twenty-eight, rain or shine.
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And on leap years, twenty-nine.
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A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.
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How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
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https://projecteuler.net/problem=19
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*/
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enum Month {JANUARY=1,FEBRUARY,MARCH,APRIL,MAY,JUNE,JULY,AUGUST,SEPTEMBER,OCTOBER,NOVEMBER,DECEMBER};
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int DaysInMonth(enum Month month,int year) {
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switch (month) {
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case JANUARY:
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case MARCH:
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case MAY:
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case JULY:
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case AUGUST:
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case OCTOBER:
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case DECEMBER:{
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return 31;
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}break;
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case APRIL:
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case JUNE:
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case SEPTEMBER:
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case NOVEMBER:{
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return 30;
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}break;
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case FEBRUARY:{
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return ((year%100==0)&&(year%400!=0))?28:(year%4==0)?29:28;
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}break;
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}
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}
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int main(int argc,char**argv) {
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int day=1;
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enum Month month=1;
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int year=1900;
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enum Weekday{
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SUNDAY,
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MONDAY,
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TUESDAY,
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WEDNESDAY,
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THURSDAY,
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FRIDAY,
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SATURDAY,
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} weekday=MONDAY;
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int sundayCount=0;
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while((day!=31)||(month!=12)||(year!=2000)) {
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printf("Date: %d/%d/%d\n",month,day,year);
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if (year>=1901) {
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//Start counting Sundays.
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if (weekday==SUNDAY&&day==1) {
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sundayCount++;
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}
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}
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//Increment the day.
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if (day+1<=DaysInMonth(month,year)) {
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day++;
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} else
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if (month+1<=12){
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//It's a new month.
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month++;
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day=1;
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} else {
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//It's a new year!
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year++;
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day=1;
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month=1;
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//printf("The year is now %d...\n",year);
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}
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weekday=((weekday+1)<=SATURDAY)?weekday+1:SUNDAY;
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}
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printf("\n\n%d Sundays were on the 1st of the month.",sundayCount);
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return 0;
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}
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