Merge pull request #431 from itayfry/balanced-parens-stack-python

Balanced Parenthesis problem in Python

Author: iam-abbas

Stack Algorithms/Balanced Parenthesis Problem/Python/balanced_parenthesis.py

@@ -0,0 +1,21 @@
+def balanced(string): 
+    opening_parens = [ '(', '[', '{' ]
+    closing_parens = [ ')', ']', '}' ]
+    parens_dict = dict(zip(opening_parens, closing_parens))
+    
+    stack = []
+    for char in string:
+        if char in opening_parens:
+            stack.append(char)
+        elif char in closing_parens:
+            if not stack or char != parens_dict[stack.pop()]:
+                return False
+    return not stack
+
+if __name__ == '__main__':
+    balanced_expression = '{[()()[]{}((()))]}'
+    print balanced(balanced_expression)
+    imbalanced_expression = '{[()()[]{}((()))]}}'
+    print balanced(imbalanced_expression)
+    invalid_expression = '{[()()[]{}((()))]}}{'
+    print balanced(invalid_expression)