For a binary tree T, we can define a flip operation as follows: choose any node, and swap the left and right child subtrees.

A binary tree X is flip equivalent to a binary tree Y if and only if we can make X equal to Y after some number of flip operations.

Given the roots of two binary trees `root1` and `root2`, return `true` if the two trees are flip equivalent or `false` otherwise.

Example 1:

    Input: root1 = [1,2,3,4,5,6,null,null,null,7,8], root2 = [1,3,2,null,6,4,5,null,null,null,null,8,7]
    Output: true
    Explanation: We flipped at nodes with values 1, 3, and 5.

Example 2:

    Input: root1 = [], root2 = []
    Output: true

Example 3:

    Input: root1 = [], root2 = [1]
    Output: false

Constraints:

- The number of nodes in each tree is in the range `[0, 100]`.
- Each tree will have unique node values in the range `[0, 99]`.