Valid Parentheses

题目描述

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.

解题思路

很常见的括号匹配问题，第一时间想到栈的用法。

Python 中可以借助于列表的 append()、pop() 方法来实现。

即如果列表为空或者不匹配，那么就压入栈，否则就弹出。

def isValid(self, s):
    """
    :type s: str
    :rtype: bool
    """
    stack = []
    for i in s:
        if len(stack) > 0 and self.match(stack[-1], i):
            stack.pop()
        else:
            stack.append(i)
    if len(stack) == 0:
        return True
    else:
        return False