Given an integer `n`, return a list of all possible full binary trees with `n` nodes. Each node of each tree in the answer must have `Node.val == 0`.

Each element of the answer is the root node of one possible tree. You may return the final list of trees in any order.

A full binary tree is a binary tree where each node has exactly `0` or `2` children.

Example 1:

    Input: n = 7
    Output: [[0,0,0,null,null,0,0,null,null,0,0],[0,0,0,null,null,0,0,0,0],[0,0,0,0,0,0,0],[0,0,0,0,0,null,null,null,null,0,0],[0,0,0,0,0,null,null,0,0]]

Example 2:

    Input: n = 3
    Output: [[0,0,0]]

Constraints:

- `1 <= n <= 20`