LeetCode 20: Valid Parentheses

class Solution {
    public boolean isValid(String s) {
        if (s.length() % 2 == 1) {
            return false;
        }
        
        Stack<Character> stack = new Stack<>();
        for (char c : s.toCharArray()) {
            if (c == '(' || c == '[' || c == '{') {
                stack.push(c);
            } else {
                if (!stack.isEmpty() && (c == ')' && stack.peek() == '(' || c == ']' && stack.peek() == '[' || c == '}' && stack.peek() == '{')) {
                    stack.pop();
                } else {
                    return false;
                }
            }
        }
        return stack.isEmpty();
    }
}