I'm still struggling with data structures. Linked lists, stacks, queues, heaps, and recursion generally make sense to me, but binary trees haven't clicked—especially the recursive approach. Could you recommend a good way to practice or a guide that explains binary tree recursion clearly?
4 Answers
Paper tracing is surprisingly effective here. Pick a tree with only three or four nodes and follow the function step by step, including the calls that receive null children. Once you can predict the order in which nodes are visited, more complicated binary-tree problems become much less mysterious.
For a basic traversal, think of recursion as doing the same job on the current node’s left and right children. Check for a null node first, process the current node, then call the function on the left child and the right child. Each call handles one smaller subtree until there’s nothing left to visit.
Don’t start with difficult coding challenges immediately. Draw very small trees and trace the call stack for preorder, inorder, and postorder traversals. Write down when each call starts and returns. After that, practice simple tasks like finding height, depth, or counting leaves and nodes.
Try implementing the structure yourself instead of only reading about it. If you understand linked lists and can write a binary search, building a binary tree should feel much more manageable. Working with the nodes and pointers directly usually makes the recursive operations easier to understand.
The idea of treating each child as a smaller subtree helps. I think I was trying to understand the entire tree at once instead of focusing on one call.