Create number-of-days-between-two-dates.py

Author: kamyu104

Python/number-of-days-between-two-dates.py

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+# Time:  O(1)
+# Space: O(1)
+
+class Solution(object):
+    def __init__(self):
+        def dayOfMonth(M):
+            return (28 if (M == 2) else 31-(M-1)%7%2)
+
+        self.__lookup = [0]*12
+        for M in xrange(1, len(self.__lookup)):
+            self.__lookup[M] += self.__lookup[M-1]+dayOfMonth(M)
+
+    def daysBetweenDates(self, date1, date2):
+        """
+        :type date1: str
+        :type date2: str
+        :rtype: int
+        """
+        def num_days(date):
+            Y, M, D = map(int, date.split("-"))
+            leap = 1 if M > 2 and (((Y % 4 == 0) and (Y % 100 != 0)) or (Y % 400 == 0)) else 0
+            return (Y-1)*365 + ((Y-1)//4 - (Y-1)//100 + (Y-1)//400) + self.__lookup[M-1]+D+leap
+     
+        return abs(num_days(date1) - num_days(date2))
+
+
+# Time:  O(1)
+# Space: O(1)
+import datetime
+
+
+class Solution2(object):
+    def daysBetweenDates(self, date1, date2):        
+        delta = datetime.datetime.strptime(date1, "%Y-%m-%d")
+        delta -= datetime.datetime.strptime(date2, "%Y-%m-%d")
+        return abs(delta.days)