【LeetCode】LeetCode——第20题：Valid Parentheses

20. Valid Parentheses

   

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Total Accepted: 106450 Total Submissions: 361988 Difficulty: Easy

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

题目的大概意思是：给定一个括号字符串s，判断该字符串括号是否是有效的。

这道题难度等级：简单

思路：对字符串进行逐一判断，使用堆栈的思想可以做。当然，为了用空间换取时间，我这里做了一个表，使用查表法即可。

class Solution {public:    bool isValid(string s) {vector<char> tmp;vector<char> table(255, 0);table['('] = table[')'] = 1;table['['] = table[']'] = 2;table['{'] = table['}'] = 3;int i = 0;for (i = 0; i < s.length(); ++i){if (s[i] == '(' || s[i] == '[' || s[i] == '{'){tmp.push_back(s[i]);}else if (s[i] == ')' || s[i] == ']' || s[i] == '}'){if (tmp.empty() || table[s[i]] != table[tmp[tmp.size() - 1]]){return false;}tmp.pop_back();}}return tmp.empty() ? true : false;    }};

提交代码，AC掉，Runtime:0ms。