week 6: valid parentheses

Author: prograsshopper

valid-parentheses/prograsshopper.py

@@ -0,0 +1,23 @@
+class Solution:
+    def isValid(self, s: str) -> bool:
+        # time complexity: O(n)
+        # space complexity: O(n)
+        opens = ['(', '[', '{']
+        closes = [')', ']', '}']
+        required = []
+        pair = {
+            '(': ')',
+            '[': ']',
+            '{': '}'
+        }
+        answer = True
+        for elem in s:
+            if elem in opens:
+                required.append(pair[elem])
+            else:
+                if elem in required and required[-1] == elem:
+                    required.pop()
+                else:
+                    answer = False
+                    break
+        return True if (answer and len(required) == 0) else False