week 6 valid-parentheses

Author: i-mprovising

valid-parentheses/i-mprovising.py

@@ -0,0 +1,24 @@
+"""
+Time complexity O(n)
+
+stack
+"""
+class Solution:
+    def isValid(self, s: str) -> bool:
+        open_brackets = ["(", "{", "["]
+        bracket_map = {"(":")", "{":"}", "[":"]"}
+        stack = []
+        for char in s:
+            if char in open_brackets:
+                stack.append(char)
+                continue
+            if not stack:
+                return False
+            open_b = stack.pop() # last in open bracket
+            if bracket_map[open_b] != char:
+                return False
+        if stack:
+            return False
+        return True
+            
+