解决思路

动态规划

 public int rob(TreeNode root) {
        int[] result = robInternal(root);
        return Math.max(result[0],result[1]);
    }
    private int[] robInternal(TreeNode root){
        if (root == null)
            return new int[2];
        int[] result = new int[2];
        int[] left = robInternal(root.left);
        int[] right = robInternal(root.right);
        result[0] = Math.max(left[0],left[1]) + Math.max(right[0],right[1]);
        result[1] = left[0] + right[0] + root.val;
        return result;
    }