use stack to solve parenthesis matching

Author: HaFred

python/020_Valid_Parentheses.py

@@ -1,6 +1,6 @@
 # class Solution(object):
 #     def isValid(self, s):
-        
+
 #
 class Solution:
     def isValid(self, s):
@@ -40,6 +40,23 @@ def isValid(self, s):
         else:
             return False
 
+    def isValid_stack(self, s):
+        stack = []
+        for i in s:
+            if i in ['(', '{', '[']:
+                stack.append(i)
+            else:
+                if len(stack) == 0:
+                    return False
+                out_stack = stack.pop()
+                if not ((out_stack == '(' and i == ')') or \
+                        (out_stack == '[' and i == ']') or \
+                        (out_stack == '{' and i == '}')):
+                    return False
+        if len(stack) != 0:  # make sure it is not single side column
+            return False
+        else:
+            return True
 
     # def isValid(self, s):
     #     # python replace
@@ -57,3 +74,11 @@ def isValid(self, s):
     #         return True
     #     else:
     #         return False
+
+
+if __name__ == '__main__':
+    sinput = "()[]{}"
+    gt = True
+    s = Solution()
+    out = s.isValid_stack(sinput)
+    print(out)