# Project Euler: Problem 19

By | 3. April 2015

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 Problem19 {

public static void main(String[] args) {

int[] months = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
int days = 0;
int sundays = 0;

for (int i = 1901; i <= 2000; i++) {
for (int j = 0; j < months.length; j++) {
if (days % 7 == 0) {
sundays++;
}
if (j == 1 && isLeapYear(i)) {
days += 29;
} else {
days += months[j];
}

}
}
System.out.println(sundays);

}
public static boolean isLeapYear(int year) {
return ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);
}
}```

Lösung: 171