Problem 019

git-svn-id: file:///srv/svn/euler@46 e5f4c3ec-3c0c-11df-b522-21efaa4426b5

e019.py

@@ -0,0 +1,30 @@
+class Day:
+    SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY = range(7)
+
+def is_leap_year(year):
+    return (year % 100 > 0 and year % 4 == 0) or (year % 400 == 0)
+
+year = 1900
+# 1/1/1900 was a Monday
+first_day = Day.MONDAY
+
+total = 0
+while year < 2000:
+    year = year + 1
+    # Count last year's days to advance the starting weekday
+    days = 366 if is_leap_year(year - 1) else 365
+    # List the number of days in each month for this year
+    months = [
+        31,
+        29 if is_leap_year(year) else 28,
+        31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+    ]
+    first_day = (first_day + days % 7) % 7
+    sundays = 0
+    for m in range(len(months)):
+        days = sum(months[:m])
+        first_sunday = (7 - ((first_day + days % 7) % 7)) % 7 + 1
+        if first_sunday == 1:
+            total = total + 1
+
+print 'Total months beginning on Sunday from 1/1/1901 to 12/31/2000: {0}'.format(total)