leet_20_Valid_Parentheses.py

最新推荐文章于 2020-01-23 16:54:58 发布

wonengguwozai

最新推荐文章于 2020-01-23 16:54:58 发布

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分类专栏：刷刷题

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本文介绍了一个简单的Python程序，用于检查包含括号的字符串是否有效。有效的字符串需要满足：相同类型的括号必须正确闭合，且闭合顺序正确。文章通过两个不同的Python函数实现这一功能，并提供了示例代码。

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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.

Example 1:

Input: "()"
Output: true

def valid(parentheses):
    pairs_list = []
    par = ["([{", ")]}"]
    for i in parentheses:
        if i in par[0]:
            pairs_list.append(i)
        elif i in par[1] and not len(pairs_list):
                return False
        elif i in par[1] and pairs_list[len(pairs_list) - 1] == par[0][par[1].index(i)]:
            pairs_list.pop()
        else:
            pass
    if len(pairs_list):
        return False
    else:
        return True


if __name__ == "__main__":
    parentheses = input("please input the parentheses")
    print("valid is :", valid(parentheses))

more pythonic:

def valid(parentheses):
    map = {')': '(', ']': '[', '}': '{'}
    list = []
    for e in parentheses:
        if e in map and (list and list[-1] == map[e]):
            list.pop()
        else:
            list.append(e)
            #print(e)
    return not list