LeetCode（20）Valid Parentheses

题目

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.

分析

典型的括号匹配问题，数据结构一书中的典型实例。其程序实现，借助栈结构是最佳方法。

AC代码

class Solution {public:    bool isValid(string s) {        int len = strlen(s.c_str());        if (len == 0)            return true;        if (len % 2 != 0)            return false;        //括号匹配问题，用数据结构栈辅助实现        stack<char> sta;        for (int i = 0; i < len; i++)        {            if (s[i] != ')' && s[i] != ']' && s[i] != '}')                sta.push(s[i]);            else            {                if (sta.size() <= 0)                    return false;                if (s[i] == PairLetter(sta.top()))                    sta.pop();                else                    return false;            }//else        }//for        if (sta.size() == 0)            return true;        else            return false;    }    char PairLetter(const char &c)    {        switch (c)        {        case '(':            return ')'; break;        case '[':            return ']'; break;        case '{':            return '}'; break;        default:            return 0; break;        }    }};

GitHub测试程序源码