[Level 2] 올바른 괄호

import java.util.*;

class Solution {
    boolean solution(String s) {
        Stack<Character> stack = new Stack<>();
        
        for(int i=0; i<s.length(); i++) {
            char c = s.charAt(i);
            if(c=='(') {
                stack.push(c);
            } else {
                if(stack.isEmpty()) { return false; }
                else { stack.pop(); }
            }
        }
        
        return stack.isEmpty();
    }
}