In various traversal methods of binary trees, under the 'ITERATIVE' mode, sometimes a stack is used and other times a queue, which may lead to potential inconsistencies in the order compared to the 'RECURSIVE' mode.

[zrwusa]

Describe the bug
In various traversal methods of binary trees, under the 'ITERATIVE' mode, sometimes a stack is used and other times a queue, which may lead to potential inconsistencies in the order compared to the 'RECURSIVE' mode.

For example: the leaves method.