Add solution for challenge #17

Author: Mauricio Klein

challenge-17/Makefile

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+test:
+	python test_*.py
+
+.PHONY: test

challenge-17/README.md

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+# Longest Substring Without Repeating Characters
+
+This problem was asked by Microsoft.
+
+## Description
+
+Given a string, find the length of the longest substring without repeating characters.
+
+## Example
+
+```
+"abrkaabcdefghijjxxx" => 10
+```

challenge-17/__init__.py

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+class Solution:
+    def lengthOfLongestSubstring(self, s):
+        h = {}
+        head, tail = 0, -1
+        max_length = 0
+
+        while head < len(s):
+            if s[head] in h:
+                tail = max(tail, h[s[head]])
+            
+            h[s[head]] = head
+            max_length = max(max_length, head - tail)
+            head += 1
+
+        return max_length

challenge-17/solver.py

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+import unittest
+from solver import Solution
+
+class TestSolver(unittest.TestCase):
+    def test_solver(self):
+        self.assertEqual(Solution().lengthOfLongestSubstring("abrkaabcdefghijjxxx"), 10)
+        self.assertEqual(Solution().lengthOfLongestSubstring("abcdefghij"), 10)
+        self.assertEqual(Solution().lengthOfLongestSubstring("aaaaaaaaaa"), 1)
+        self.assertEqual(Solution().lengthOfLongestSubstring(""), 0)
+
+if __name__ == "__main__":
+    unittest.main()