chapter 1 hackerrank exercises

11/04

01. Arrays and strings/hackerrank/alternating_characters.py

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+# Algorithms > Strings > Alternating Characters 
+# https://www.hackerrank.com/challenges/alternating-characters
+
+import unittest
+
+def alternatingCharacters(s):
+    if len(set(s)) == 1:
+        return len(s) - 1
+
+    res = len(s) - max(s.count("AB"), s.count("BA"))*2
+    if s[0] == s[-1]:
+        res -= 1
+    return res
+
+class Test(unittest.TestCase):
+
+    data = [('AAAA', 3),
+            ('BBBBB', 4),
+            ('ABABABAB', 0),
+            ('BABABA', 0),
+            ('AAABBB', 4),
+            ('ABABABAA', 1)]
+
+
+    def test(self):
+        for test_string, expected in self.data:
+            res = alternatingCharacters(test_string)
+            self.assertEqual(res, expected)
+
+if __name__ == "__main__":
+    unittest.main()

01. Arrays and strings/hackerrank/funny_string.py

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+# Algorithms > Strings > Funny string
+# https://www.hackerrank.com/challenges/funny-string/
+
+import unittest
+
+def funnyString(s):
+    if len(s) < 2:
+        return "Funny"
+    
+    for i in range(1,len(s)//2):
+        if abs(ord(s[i]) - ord(s[i-1])) != abs(ord(s[-i]) - ord(s[-i-1])):
+            return "Not Funny"
+
+    return "Funny"
+
+class Test(unittest.TestCase):
+
+    data = [('acxz', 'Funny'),
+            ('bcxz', 'Not Funny'),
+            ('bcccd', 'Funny')]
+
+    def test(self):
+        for test_string, expected in self.data:
+            res = funnyString(test_string)
+            self.assertEqual(res, expected)
+
+if __name__ == "__main__":
+    unittest.main()

01. Arrays and strings/hackerrank/reduce_to_palindrome.py

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+# Algorithms > Strings > The Love-Letter Mystery
+# https://www.hackerrank.com/challenges/the-love-letter-mystery
+
+import unittest
+
+def theLoveLetterMystery(s):
+    
+    if len(s) == 1:
+        return 0
+    
+    count = 0
+    for i in range(len(s)//2):
+        count += abs(ord(s[i]) - ord(s[-1-i]))
+
+    return count
+
+class Test(unittest.TestCase):
+
+    data = [('abc', 2),
+            ('abcba', 0),
+            ('abcd', 4),
+            ('cba', 2)]
+
+
+    def test(self):
+        for test_string, expected in self.data:
+            res = theLoveLetterMystery(test_string)
+            self.assertEqual(res, expected)
+
+if __name__ == "__main__":
+    unittest.main()