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.

Valid Parentheses.cpp

class Solution {
public:
    bool isValid(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        stack<char> checker;
        
        for(int i = 0; i < s.length() ; ++i) {
            char cur = s[i];
            if(isLeft(cur)) {
                checker.push(cur);
            } else {
                if(!checker.empty() and cur == checker.top()) {
                    checker.pop();
                } else {
                    return false;
                }
            }
        }
        
        if(checker.empty()) {
            return true;
        } else {
            return false;
        }
    }
    
    
    bool isLeft(char& cur) {
        switch(cur) {
            case '(':
                cur = ')';
                break;
            case '[':
                cur = ']';
                break;
            case '{':
                cur = '}';
                break;
            default:
                return false;            
                
        }
        
        return true;
    }
};