19 Counting Sundays - Project Euler

9package xxx.xxx.xxx;

import java.util.ArrayList;

/*

 * You are given the following information, but you may prefer to do some research for yourself.

 * 1 Jan 1900 was a Monday.

 * Thirty days has September,April, June and November.

 * All the rest have thirty-one,

 * Saving February alone,

 * Which has twenty-eight, rain or shine.

 * And on leap years, twenty-nine.

 * A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.

 * How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?

 */

public class CountingSundays {

private void simpleCompute2(int standardYear, int standardMonth,int startYear,int startMonth, int endYear, int endMonth){
int year = standardYear;
int daysInANormalYear = 365;
int daysInALeapYear = 366;
int leapYearCount = 0;
int normalYearCount = 0;
ArrayList<Integer> firstDays = new ArrayList<Integer>();
int sum = 0;
while(year<=endYear){

if((year%4==0&&year%100!=0)||year%400==0){
firstDays.add(normalYearCount*365+leapYearCount*366+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+30+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+30+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+30+31+30+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+31+30+31+30+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+31+30+31+30+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+30+31+31+30+31+30+31+29+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+30+31+31+30+31+30+31+29+31+1);
sum += daysInALeapYear;
leapYearCount++;
}else{
firstDays.add(normalYearCount*365+leapYearCount*366+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+30+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+30+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+30+31+30+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+31+30+31+30+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+31+30+31+30+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+31+30+31+31+30+31+30+31+28+31+1);
firstDays.add(normalYearCount*365+leapYearCount*366+30+31+30+31+31+30+31+30+31+28+31+1);
sum += daysInANormalYear;
normalYearCount++;
}
year++;
}

// System.out.println(firstDays);

// System.out.println(firstDays.size());

int sundaysOnTheFirstOfAmonth = 0;
int startIndex = (startYear-standardYear)*12+startMonth-standardMonth;

for(int i = startIndex; i<firstDays.size();i++){
if(firstDays.get(i)%7==0){
sundaysOnTheFirstOfAmonth++;

// System.out.println(firstDays.get(i));
}
}

System.out.println("sundaysOnTheFirstOfAmonth "+sundaysOnTheFirstOfAmonth);
}

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
CountingSundays countingSundays =new CountingSundays();
countingSundays.simpleCompute2(1900,1,1901,1,2000,12);
}

}