[問題] leecode20. Valid Parentheses

[Kuba4ma ()]

題目:
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.



code:
class Solution(object):
    def isValid(self, s):
        """
        :type s: str
        :rtype: bool
        """
        stack=list()
        length=len(s)
        if length%2!=0:
            return False
        else:
            for i in range(length):
                if "(" or "{" or "[" == s[i]:
                    stack.append(s[i])
                elif ")"  == s[i]:
                    if stack.pop() != "(":
                        return False
                elif "}"  == s[i]:
                    if stack.pop() != "{":
                        return False
                elif "]"  == s[i]:
                    if stack.pop() != "[":
                        return False
            if len(stack)!=0:
                return False
            else:
                return True



input是"()"會跑出False

不知道哪裡出了問題

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→ Hsins: len("()") = 2
推 TitanEric: 建議判斷list是不是空的改成 if list,這表示存在
→ Hsins: 問題在你的 or 那邊
→ Hsins: if "(" or "{" or "[" == s[i]:
→ Hsins: 判斷的是 if "(", if "{" 和 if "[" == s[i]
→ Hsins: 前兩個永遠都是 true
→ Hsins: 你寫的其他條件根本不會走進去
→ alvinlin: 這應該用堆疊做吧
→ alvinlin: 左向括號push右向pop
→ alvinlin: Pop前確定是同對等的括號
→ alvinlin: 原來已經用堆疊做了。My bad
→ lericee: H大已講 or的兩邊True會進if 你or的兩邊是什麼
→ lericee: 可以改成s[i] in ['[','{','(']
→ Kuba4ma: 謝謝H大 已解決