OlympiadCode/leetcode_py/20.py

# give a string s containing just '(', ')' and else
# determine if the input is valid


class Solution:
    def isValid(self, s: str) -> bool:
        """
        # too slow
        symbol_dict = {"(": ")", "{": "}", "[": "]"}
        stack = []
        for i in s:
            try:
                stack_top = stack.pop()
            except IndexError:
                stack.append(i)
                continue

            try:
                if symbol_dict[stack_top] == i:
                    continue

                 stack.append(stack_top)

            except KeyError:
                return False

            stack.append(i)

        if stack:
            return False

        return True
        """

        # Optimized solution
        bracket_map = {")": "(", "}": "{", "]": "["}
        stack = []

        for char in s:
            if char in bracket_map:
                top_element = stack.pop() if stack else "#"

                if bracket_map[char] != top_element:
                    return False

            else:
                stack.append(char)

        return not stack