20. Valid Parentheses

最新推荐文章于 2024-02-05 23:11:57 发布

转载最新推荐文章于 2024-02-05 23:11:57 发布 · 71 阅读

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原文链接：http://www.cnblogs.com/huwtylv/p/9338646.html

本文介绍了一种使用栈和映射表来验证包含括号的字符串是否有效的算法。该算法确保每种类型的开括号都能被正确关闭，并按正确的顺序进行。通过具体的代码实现和示例，展示了如何判断括号序列的有效性。

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

class Solution {
public:
    bool isValid(string s) {
        stack<char> sta;
        map<char, char> mp;
        mp['('] = ')'; mp['['] = ']'; mp['{']='}';
        int n = s.size();
        for(int i=0; i<n; i++) {
            if(s[i] == '(' || s[i] == '[' || s[i] == '{')
                sta.push(s[i]);
            if(s[i] == ')' || s[i] == ']' || s[i] == '}')
                if(sta.empty() || s[i] != mp[sta.top()])
                    return false;
                else
                    sta.pop();

        }
        if(sta.empty())
            return true;
        else
            return false;
    }
};