解題思路

此處撰寫解題思路
碰到左括號推入棧
碰到右括號時，把棧頂元素拿出來看是不是配對
遍歷完字符串棧不空表明有沒有被匹配的左括號
https://leetcode-cn.com/problems/valid-parentheses/

代碼

class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        match = {
            '}': '{',
            ']': '[',
            ')': '(',
        }
        stack = []
        idx, length = 0, len(s)
        while idx < length:
            if s[idx] in '([{':
                stack.append(s[idx])
                idx += 1
            else:
                if not stack:
                    return False
                elif stack.pop() != match[s[idx]]:
                    return False
                else:
                    idx += 1
        return len(stack) == 0