EASY NC#47 Blind #60 Trees

104. Maximum Depth of Binary Tree

📖 Problem

Given the root of a binary tree, return its maximum depth. A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

🧠 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
  • •Recursive stack flow
  • •Cycle prevention
  • •Post-order reasoning

Logical Thinking Concepts

  • •Define invariants before coding
  • •Check edge cases first (`[]`, single element, duplicates)
  • •Estimate time/space before implementation
  • •Apply DFS reasoning pattern
  • •Apply BFS reasoning pattern
  • •Apply Recursion reasoning pattern

💡 Approach

  • → Use DFS recursively to find maximum depth
  • → Base case: null node has depth 0
  • → Max depth = 1 + max(depth of left, depth of right)
  • → Time: O(n), Space: O(h) where h is tree height

🛠️ Hints & Pitfalls

Hints

  • •Use DFS recursively to find maximum depth
  • •Base case: null node has depth 0
  • •Max depth = 1 + max(depth of left, depth of right)

Common Pitfalls

  • •Time: O(n), Space: O(h) where h is tree height

🧪 Test Cases

Hidden tests on submit: 3

Test Case 1
Not run
Input:
maxDepth(buildTree([3,9,20,null,null,15,7]));
Expected:
3
Test Case 2
Not run
Input:
maxDepth(buildTree([1,null,2]));
Expected:
2
Test Case 3
Not run
Input:
maxDepth(buildTree([]));
Expected:
0

📝 Code Editor

📚 Reference Solution

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🔗 Related Problems

#98 Validate Binary Search Tree #100 Same Tree #105 Construct Binary Tree from Preorder and Inorder Traversal #110 Balanced Binary Tree #124 Binary Tree Maximum Path Sum
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