public class Solution {
    public boolean isValid(String s) {
        Stack<Character> stack = new Stack<Character>();
        
        for(int i=0; i< s.length(); i++){
            if(!stack.isEmpty()){
                char c = stack.peek();
                if(match(c, s.charAt(i))){
                    stack.pop();
                }else{
                    stack.push(s.charAt(i));
                }
            }else{
                stack.push(s.charAt(i));
            }
        }
        
        if(stack.isEmpty()){
            return true;
        }else{
            return false;
        }
    }
    
    public boolean match(char a, char b){
        if( a == ‘(‘ && b == ‘)‘){
            return true;
        }else if( a == ‘[‘ && b == ‘]‘){
            return true;
        }else if( a == ‘{‘ && b == ‘}‘){
            return true;
        }
        
        return false;
    }
}