Problem 19

0019.py

@@ -0,0 +1,72 @@
+target = 171
+
+def is_leap_year (year):
+    return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)
+
+def days_since_1900 (year, month = 1, day = 1):
+    days = 0
+
+    for y in range(1900, year):
+        if (is_leap_year(y)):
+            days += 366
+        else:
+            days += 365
+
+    for m in range(1, month):
+        days += get_days_in_month(m, year)
+
+    days += day - 1
+
+    return days
+
+days_in_month = [
+    None,
+    31,
+    28,
+    31,
+    30,
+    31,
+    30,
+    31,
+    31,
+    30,
+    31,
+    30,
+    31,
+]
+
+week_days = [
+    'mon',
+    'tue',
+    'wed',
+    'thu',
+    'fri',
+    'sat',
+    'sun',
+]
+
+def get_days_in_month (month, year):
+    days = days_in_month[month]
+
+    if (month == 2 and is_leap_year(year)):
+        return days + 1
+
+    return days
+
+def get_day_of_week (year, month, day):
+    days = days_since_1900(year, month, day)
+
+    rest = days % 7
+
+    return week_days[rest]
+
+
+count = 0
+
+for year in range(1901, 2001):
+    for month in range(1, 13):
+        if (get_day_of_week(year, month, 1) == 'sun'):
+            count += 1
+
+print(count)
+print(count == target)