Added Valid Parantheses solution to python folder

python/valid_parentheses.py

@@ -0,0 +1,52 @@
+"""
+Problem statement:
+Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
+
+An input string is valid if:
+
+1. Open brackets must be closed by the same type of brackets.
+2. Open brackets must be closed in the correct order.
+3. Every close bracket has a corresponding open bracket of the same type.
+
+"""
+class Solution:
+    def isValid(self, s):
+        """
+        :type s: str
+        :rtype: bool
+        """
+        # create a stack to the brackets
+        stacks = []
+
+        # define the brackets and their corresponding pairs
+        brackets = {')': '(', '}': '{', ']': '['}
+
+        # iterate over each character in the string
+        for char in s:
+            # if the character is an open bracket, push it to the stack
+            if char in brackets.values():
+                stacks.append(char)
+            # if the character is a close bracket
+            else:
+                # if the stack is empty or the top of the stack does not match the corresponding open bracket, return False
+                if not stacks or brackets[char] != stacks.pop():
+                    return False
+
+        # if the stack is empty, the string is valid
+        return not stacks
+
+
+# Example usage:
+"""
+Input: s = "()"
+Output: true
+
+Input: s = "()[]{}"
+Output: true
+
+Input: s = "(]"
+Output: false
+
+Input: s = "([)]"
+Output: false
+"""