872. Leaf-Similar Trees

naive比较法，效率比较低，还有一种同时比较的方法，记得去看。

public boolean leafSimilar(TreeNode root1, TreeNode root2) {
    List<Integer> res1 = new ArrayList<>(),
                    res2 = new ArrayList<>();
    findLeaf(root1, res1);
    findLeaf(root2, res2);
    return res1.equals(res2);
}

public void findLeaf(TreeNode root, List<Integer> res) {
    if (root == null) return;
    if (root.left == null && root.right == null) res.add(root.val);
    findLeaf(root.left, res);
    findLeaf(root.right, res);
}