leetcode—Valid Parentheses

1.问题描述

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.

2.解法分析

典型的栈用法。

class Solution {

public:

    bool isValid(string s) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        vector<char> myStack;

        map<char,char>dict;

        dict.insert(make_pair('(',')'));

        dict.insert(make_pair('[',']'));

        dict.insert(make_pair('{','}'));

        for(int i=0;i<s.length();++i)

        {

            if(s[i]=='('||s[i]=='['||s[i]=='{')myStack.push_back(s[i]);

            else

                if(s[i]==')'||s[i]==']'||s[i]=='}')

                {

                    if(myStack.empty())return false;

                    if(dict[myStack.back()]==s[i])myStack.pop_back();

                    else return false;

                }

        }

        if(myStack.empty())return true;

        return false;

    }

};