Adding some trees problems.

[PiyushK79]

@gauriiighadge I would like to add some problems related to trees like kth ancestor, flatten to linked list etc. Please assign this task to me under Hacktoberfest2023.

[sumitverma107]

Hi @gauriiighadge please assign this to me,i would love to work on this.

[saku1331]

I wish to contribute. Kindly assign this to me.

[AhanaDatta59]

Respected Sir, Having a very problem solving mindset, I can add extremely intriguing and brain racking problem on trees. Kindly assign me with this task. Here is the link to my leetcode account: https://leetcode.com/Ahanadatta59/

[rahuldewangan275]

hello sir can you assign this to me under #Hactoberfest