Valid Parentheses - C++ stack clean 10 line solution

Easy     Stack     String    

Problem Statement:

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

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.
3. Every close bracket has a corresponding open bracket of the same type.

 

Example 1:

Input: s = "()"
Output: true

Example 2:

Input: s = "()[]{}"
Output: true

Example 3:

Input: s = "(]"
Output: false

 

Constraints:

• 1 <= s.length <= 104
• s consists of parentheses only '()[]{}'.

Solution:

class Solution {
public:
    bool isValid(string s) 
    {
        stack<char>stk;
        unordered_map<char,char>map{ {'(',')'},{'{','}'},{'[',']'} };
        for (char ch: s)
        {
            if (map.count(ch)) stk.push(ch);
            else
            {
                if (stk.empty() || map[stk.top()]!=ch)
                    return false;
                stk.pop();
            }
        }
        return stk.empty();
    }
};