generate_parenthesis (keon#384)

* generate_parenthesis

* format

Author: RenliangShi

algorithms/backtrack/generate_parenthesis.py

@@ -14,16 +14,30 @@
 """
 
 
-def generate_parenthesis(n):
+def generate_parenthesis_v1(n):
     def add_pair(res, s, left, right):
         if left == 0 and right == 0:
             res.append(s)
             return
         if right > 0:
-            add_pair(res, s+")", left, right-1)
+            add_pair(res, s + ")", left, right - 1)
         if left > 0:
-            add_pair(res, s+"(", left-1, right+1)
+            add_pair(res, s + "(", left - 1, right + 1)
 
     res = []
     add_pair(res, "", n, 0)
     return res
+
+
+def generate_parenthesis_v2(n):
+    def add_pair(res, s, left, right):
+        if left == 0 and right == 0:
+            res.append(s)
+        if left > 0:
+            add_pair(res, s + "(", left - 1, right)
+        if right > 0 and left < right:
+            add_pair(res, s + ")", left, right - 1)
+
+    res = []
+    add_pair(res, "", n, n)
+    return res

tests/test_backtrack.py

@@ -11,6 +11,7 @@
 )
 
 import unittest
+from algorithms.backtrack.generate_parenthesis import *
 
 
 class TestAddOperator(unittest.TestCase):
@@ -170,3 +171,16 @@ def test_pattern_match(self):
         self.assertTrue(pattern_match(pattern1, string1))
         self.assertTrue(pattern_match(pattern2, string2))
         self.assertFalse(pattern_match(pattern3, string3))
+
+class TestGenerateParenthesis(unittest.TestCase):
+
+    def test_generate_parenthesis(self):
+        self.assertEqual(generate_parenthesis_v1(2), ['()()', '(())'])
+        self.assertEqual(generate_parenthesis_v1(3), ['()()()', '()(())', '(())()', '(()())', '((()))'])
+        self.assertEqual(generate_parenthesis_v2(2), ['(())', '()()'])
+        self.assertEqual(generate_parenthesis_v2(3), ['((()))', '(()())', '(())()', '()(())', '()()()'])
+
+if __name__ == '__main__':
+
+    unittest.main()
+