Merge pull request #41 from akashsara/issue36-valid-parenthesis

Added solution to issue 36 - Valid Parenthesis

intermediate/valid_parenthesis_akashsara.py

@@ -0,0 +1,22 @@
+#!python3
+
+def has_valid_parens(input_string):
+	"""
+	CHALLENGE: 
+	Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
+
+	An input string is valid if:
+    > Open brackets must be closed by the same type of brackets.
+    > Open brackets must be closed in the correct order.
+    > Note that an empty string is also considered valid.
+
+	DIFFICULTY: INTERMEDIATE [Due to use of stack]
+	"""
+	stack = []
+	bracket_map = {'[':']',	'(':')', '{':'}'}
+	for bracket in input_string:
+		if bracket in bracket_map:
+			stack.append(bracket)
+		elif len(stack) == 0 or bracket_map[stack.pop()] != bracket:
+			return False
+	return len(stack) == 0