LeetCode20:有效的括号(Valid Parentheses)-蒲公英云

LeetCode20:有效的括号(Valid Parentheses)

小灰灰 2024-04-19 08:03 140阅读 0赞

英文题目：

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:

Input: "()"
Output: true

Example 2:

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

Example 3:

Input: "(]"
Output: false

Example 4:

Input: "([)]"
Output: false

Example 5:

Input: "{[]}"
Output: true

中文题目：

给定一个只包括 ‘(’，’)’，’{’，’}’，’[’，’]’ 的字符串，判断字符串是否有效。

有效字符串需满足：

1.左括号必须用相同类型的右括号闭合。
2.左括号必须以正确的顺序闭合。

注意空字符串可被认为是有效字符串。

示例 1:

输入: "()"
输出: true

示例 2:

输入: "()[]{}"
输出: true

示例 3:

输入: "(]"
输出: false

示例 4:

输入: "([)]"
输出: false

示例 5:

输入: "{[]}"
输出: true

解答：

C++

class Solution:
    def isValid(self, s: str) -> bool:
        stack = []
        lookup = {'(':')','{':'}','[':']'}
        for parenthese in s:
            if parenthese in lookup:
                stack.append(parenthese)
            elif len(stack)==0 or lookup[stack.pop()] != parenthese:
                return False
        return len(stack)==0