Method dfs

java/0100-same-tree.java:24–39

(TreeNode p, TreeNode q)

    }

    private boolean dfs(TreeNode p, TreeNode q) {
        if (p == null && q == null) {
            return true;
        }

        if (p == null || q == null) {
            return false;
        }

        if (p.val != q.val) return false;

        boolean left = dfs(p.left, q.left);
        boolean right = dfs(p.right, q.right);

        return left && right;
    }
}