20. Valid Parentheses

2019-03-29

20. Valid Parentheses

Given a string 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.

Note that an empty string is also considered valid.

Example 1:

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Input: "()"
Output: true

Example 2:

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Input: "()[]{}"
Output: true

Example 3:

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Input: "(]"
Output: false

Example 4:

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Input: "([)]"
Output: false

Example 5:

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Input: "{[]}"
Output: true

Code:

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class Solution(object):
    # @param s, a string
    # @return a boolean
    def isValid(self, s)->bool:
        valids = ['()', '[]', '{}']
        if len(s) % 2 != 0:
            return False
        while len(s) != 0:

            o_len = len(s)
            for val in valids:
                s = s.replace(val, '')
            if len(s) == o_len:
                return False
        return True
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