驗證大小中括號是否成對閉合匹配

驗證大小中括號是否成對閉合匹配

Valid Parentheses

• 驗證大小中括號是否成對閉合匹配。
• Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’, determine if the input string is valid.
• The brackets must close in the correct order, “()” and “()[]{}” are all valid but “(]” and “([)]” are not..

example 1

input: '{{()}}'
output: True

example 2

input: '(([)])'
output: False

example 3

input: ''
output: True

思路

1. 使用棧（先進後出）
2. 如果遇到左邊符號{，[，(，則將其對應的右邊符號}，]，)入棧，如果遇到右邊符號，則判斷棧頂元素是否匹配，不匹配則返回False
3. 最後棧空，則完全閉合匹配，返回True

代碼

class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        brackets = {
            '(': ')',
            '[': ']',
            '{': '}'
        }
        stack = []
        for i in s:
            if i in brackets:
                stack.append(brackets[i])
            elif i in brackets.values():
                if len(stack) == 0 or stack.pop(-1) != i:
                    return False
        return len(stack) == 0

本題以及其它leetcode題目代碼github地址: github地址