[Python] Refactor Valid Parentheses.py

python/Stack/Valid Parentheses.py

@@ -0,0 +1,41 @@
+"""
+Given a string containing algebraic expressions with alphabets (A-Z) and specific parentheses ('(', ')', '{', '}', '[', ']'),
+determine if the input string is valid.
+
+An input string is valid if:
+    - Open brackets must be closed by the same type of brackets.
+    - Open brackets must be closed in the correct order.
+
+Examples:
+    (A+B)+(C-D)     : Valid as the expression has matching opening and closing brackets.
+    (A+B)+(C-       : Invalid as a closing bracket is missing.
+    {(A+B)+[C-D]}   : Valid as opening and closing brackets match correctly.
+    ((A+B)-[C+D]}   : Invalid as the last closing bracket does not correspond to an opening bracket.
+"""
+
+from python.Stack.Stack import Stack
+
+"""
+    Time Complexity : O(n) due to traversal of the expression string
+    Space Complexity : O(n) due to stack
+"""
+
+def check_valid_parentheses(expression):
+    stack = Stack()
+    parentheses_map = {')': '(', '}': '{', ']': '['}
+
+    for char in expression:
+        if char in parentheses_map.values():
+            stack.push(char)
+        elif char in parentheses_map:
+            if stack.is_empty() or stack.pop() != parentheses_map[char]:
+                return False
+
+    return stack.is_empty()
+
+
+if __name__ == "__main__":
+    print(check_valid_parentheses("{(A+B)+[C-D]}"))  # Valid
+    print(check_valid_parentheses("(A+B)+(C-"))  # Invalid
+    print(check_valid_parentheses("((A+B)-[C+D]}"))  # Invalid
+    print(check_valid_parentheses("}(A-B){"))  # Invalid