MEDIUM NC#48 Trees
543. Diameter of Binary Tree
📖 Problem
Given the root of a binary tree, return the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root. The length of a path between two nodes is represented by the number of edges between them.
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
- •Level-order traversal
- •Queue discipline
- •Shortest-step interpretation
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
- •Apply BFS reasoning pattern
💡 Approach
- → Diameter = longest path through any node as the highest point
- → For each node, find longest path going through it
- → This is left height + right height
- → Track max diameter across all nodes
- → Time: O(n), Space: O(h) where h is tree height
🧭 Prerequisites
🛠️ Hints & Pitfalls
Hints
- •Diameter = longest path through any node as the highest point
- •For each node, find longest path going through it
- •This is left height + right height
Common Pitfalls
- •Track max diameter across all nodes
- •Time: O(n), Space: O(h) where h is tree height
🧪 Test Cases
Hidden tests on submit: 1
Test Case 1
Not run Input:
depth(node: TreeNode | null); Expected:
Computed from hidden reference Test Case 2
Not run Input:
depth(node.left); Expected:
Computed from hidden reference Test Case 3
Not run Input:
depth(node.right); Expected:
Computed from hidden reference 📝 Code Editor
📤 Output