算法打卡Day26_leetcode _20.有效的括号

    public boolean isValid(String s) {
        Deque<Character> stack = new LinkedList<Character>();
        for (char c: s.toCharArray()) {
            if (c=='{'){
                stack.push('}');;
            }
            else if (c=='('){
                stack.push(')');
            }else if (c=='['){
                stack.push(']');
            }else  if (stack.isEmpty() || stack.pop()!= c){
                return false;
            }
        }
        return stack.isEmpty();
    }