class TreeNode {
    char val;
    TreeNode left = null;
    TreeNode right = null;

    TreeNode(char _val) {
        this.val = _val;
    }
}

// 獲取最大深度
    public static int getMaxDepth(TreeNode root) {
        if (root == null)
            return 0;
        else {
            int left = getMaxDepth(root.left);
            int right = getMaxDepth(root.right);
            return 1 + Math.max(left, right);
        }
    }

// 獲取最大寬度
    public static int getMaxWidth(TreeNode root) {
        if (root == null)
            return 0;

        Queue<TreeNode> queue = new ArrayDeque<TreeNode>();
        int maxWitdth = 1; // 最大寬度
        queue.add(root); // 入隊

        while (true) {
            int len = queue.size(); // 當前層的節點個數
            if (len == 0)
                break;
            while (len > 0) {// 如果當前層，還有節點
                TreeNode t = queue.poll();
                len--;
                if (t.left != null)
                    queue.add(t.left); // 下一層節點入隊
                if (t.right != null)
                    queue.add(t.right);// 下一層節點入隊
            }
            maxWitdth = Math.max(maxWitdth, queue.size());
        }
        return maxWitdth;
    }