leetcode/valid_parentheses at main · shelialia/leetcode · GitHub

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class Solution(object):
    # a function that returns a Boolean expression, so its either True or False
    # input is s
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """

        # if the length of the list is not even, return False as it is definitely wrong
        if (len(s)) % 2 != 0:
            return False

        # create a dictionary to store the key value pairs
        dict = {'(': ')', '{': '}', '[': ']'}
        # create an empty list
        stack = []

        for i in s:
            # use .keys() function to check if character is present in any keys of the dictionary, ie. the character must be an open bracket
            if i in dict.keys():
                stack.append(i)

            # if the character is a close bracket
            else:
                 # assign variable a to the left most value in the stack ie. an open bracket
                if stack == []:
                    return False
                a = stack.pop()

                # if the value pair of key a and the current close bracket character are not the same, return False
                if i != dict[a]:
                    return False
        if stack == []:
            return True

        return False