Excel Sheet Column Title/ Factorial Trailing Zeroes

Author: gavinfish

168 Excel Sheet Column Title.py

@@ -0,0 +1,31 @@
+'''
+Given a positive integer, return its corresponding column title as appear in an Excel sheet.
+
+For example:
+
+    1 -> A
+    2 -> B
+    3 -> C
+    ...
+    26 -> Z
+    27 -> AA
+    28 -> AB 
+'''
+
+class Solution(object):
+    def convertToTitle(self, n):
+        """
+        :type n: int
+        :rtype: str
+        """
+        result = []
+        base = ord('A')
+        while n:
+            n, r = divmod(n - 1, 26)
+            result.append(chr(base + r))
+        return ''.join(result[::-1])
+
+
+if __name__ == "__main__":
+    assert Solution().convertToTitle(1) == 'A'
+    assert Solution().convertToTitle(28) == 'AB'

172 Factorial Trailing Zeroes.py

@@ -0,0 +1,21 @@
+'''
+Given an integer n, return the number of trailing zeroes in n!.
+
+Note: Your solution should be in logarithmic time complexity.
+'''
+
+class Solution(object):
+    def trailingZeroes(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+        count = 0
+        while n:
+            n //= 5
+            count += n
+        return count
+
+
+if __name__ == "__main__":
+    assert Solution().trailingZeroes(25) == 6