abhishek-jaisingh · March 9, 2020 10:57 · Mar 9, 2020
diff --git a/project-euler-19.py b/project-euler-19.py
@@ -0,0 +1,40 @@
+# 1 Jan 1901 to 31 Dec 2000
+# 1 Jan 1900 Monday => 1 Jan 1901 => Tuesday
+month_days = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+
+def is_leap(y):
+	return y % 400 == 0 if y % 100 == 0 else y % 4 == 0
+
+def get_month_days(y, i):
+	if is_leap(y) and i == 1:
+		return 29
+	return month_days[i]
+
+def get_good_sundays(year):
+	res = 0
+	diff_years = year - 1900
+	leap_years = 0 if (diff_years <= 4 or diff_years == 100) else diff_years / 4
+	odd_days = diff_years + leap_years
+
+	curr = 1 + odd_days
+
+	for i in range(0, 12):
+		if i != 0:
+			curr += get_month_days(year, i-1)
+		curr %= 7
+
+		if curr == 0:
+			res += 1
+
+	return res
+
+
+ans = 0
+
+YEAR_START = 1901
+YEAR_END = 2000
+
+for y in range(YEAR_START, YEAR_END+1):
+	ans += get_good_sundays(y)
+
+print(ans)
No results found