20. Valid Parentheses

class Solution {
    public boolean isValid(String s) {

        if (s.length() % 2 != 0) {
            return false;
        }
        
        Map<Character, Character> set = new HashMap<Character, Character>();
        set.put(']', '[');
        set.put(')', '(');
        set.put('}', '{');
        
        Stack<Character> check = new Stack<Character>();
        
        for (int i = 0; i < s.length(); i++) {
            if (!set.containsKey(s.charAt(i))) {
                check.push(s.charAt(i));
            } else {
                if (check.isEmpty()) {
                    return false; 
                }
                if (check.pop() != set.get(s.charAt(i))) {
                    return false;
                }
            }
        }
        
        return (check.isEmpty());
    }
}

Runtime: 2 ms, faster than 23.32% of Java online submissions for Valid Parentheses.
Memory Usage: 37.4 MB, less than 20.24% of Java online submissions for Valid Parentheses.

느린데 고치기 너무 귀찮다..^^