Tree traversals and heap properties

What you’ll practice

Move confidently between preorder, inorder, postorder, and level-order traversals, and translate them into practical reasoning about recursion and queues. You’ll also test core heap rules (min-heap/max-heap), array indexing, and parent/child relationships.

Each question uses 4 options and there’s no timer, so you can slow down to validate invariants, trace steps, and catch off-by-one mistakes. Choose your question count and difficulty before starting to tailor the session to quick revision or deeper practice.

Common pitfalls to avoid

Many wrong answers come from mixing traversal outputs (especially inorder vs. preorder) or forgetting how level-order is produced with a queue. With heaps, frequent slips include incorrect 0-based vs 1-based index formulas and assuming a heap is also a BST.

• Confusing traversal names with their visit order (NLR/LNR/LRN)
• Misapplying heap property to all subtrees without checking parent-child comparisons
• Treating heaps like sorted arrays or binary search trees
• Missing edge cases: single node, skewed tree, duplicates, empty children
• Mixing 0-based and 1-based heap index calculations

How difficulty is balanced

Difficulty is mixed by design: easier items reinforce definitions and basic traces, while tougher ones combine traversal reconstruction, heapify steps, and complexity reasoning. This blend helps you build momentum early and still get meaningful challenge as you continue.