Added bubble sort implementation in Python

Author: manikonda-anjali

algorithms/valid-parentheses.py

@@ -0,0 +1,12 @@
+class Solution:
+    def isValid(self, s):
+        stack = []
+        mapping = {')': '(', '}': '{', ']': '['}
+        for char in s:
+            if char in mapping:
+                top = stack.pop() if stack else '#'
+                if mapping[char] != top:
+                    return False
+            else:
+                stack.append(char)
+        return not stack