首页 > itarticle > 20 valid parentheses

20 valid parentheses

admin 11月 14, 2020 0

Description

Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, 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.
Note that an empty string is also considered valid.

My Solution

Python

class (object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        valid_dict = {
            '(':')',
            '[':']',
            '{':'}',
            ')':'',
            ']':'',
            '}':''
        }
        stack = []
        for char in s:
            if len(stack) > 0 and (valid_dict[stack[-1]] == char):
                stack.pop()
            else:
                stack.append(char)
        if len(stack) == 0:
            return True
        else:
            return False

想法：使用栈

Other Solution

Python

class (object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        n = len(s)
        if n == 0:
            return True

        if n % 2 != 0:
            return False

        while '()' in s or '{}' in s or '[]' in s:
            s = s.replace('{}','').replace('()','').replace('[]','')

        return s == ''