[leetcode]20. Valid Parentheses

题目链接:https://leetcode.com/problems/valid-parentheses/

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.

class Solution {
public:
   bool isValid(string s)
    {
        unordered_map<char, char> map;
        map['(']=')';
        map['{']='}';
        map['[']=']';
        
        stack<char> charStack;
        for(int i=0;i<s.length();i++)
        {
            if(map.find(s[i])!=map.end())
                charStack.push(s[i]);
            else
            {
                if(!charStack.empty()&&map[charStack.top()]==s[i])
                    charStack.pop();
                else
                    return false;
            }
        }
        return charStack.empty();
    }
};