MEDIUM NC#54 Trees

199. Binary Tree Right Side View

📖 Problem

Given the root of a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.

🧠 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

  • → Use level order traversal (BFS)
  • → For each level, take the rightmost node
  • → Collect these rightmost nodes' values
  • → Time: O(n), Space: O(w) where w is max width

🧭 Prerequisites

#105 Construct Binary Tree from Preorder and Inorder Traversal #110 Balanced Binary Tree

🛠️ Hints & Pitfalls

Hints

  • •Use level order traversal (BFS)
  • •For each level, take the rightmost node
  • •Collect these rightmost nodes' values

Common Pitfalls

  • •Time: O(n), Space: O(w) where w is max width

🧪 Test Cases

Hidden tests on submit: 1

Test Case 1
Not run
Input:
rightSideView(buildTree([1,2,3,null,5,null,4]));
Expected:
[1, 3, 4]
Test Case 2
Not run
Input:
rightSideView(buildTree([1,null,3]));
Expected:
[1, 3]
Test Case 3
Not run
Input:
rightSideView(buildTree([]));
Expected:
[]

📝 Code Editor

📚 Reference Solution

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🔗 Related Problems

#98 Validate Binary Search Tree #100 Same Tree #104 Maximum Depth of Binary Tree #105 Construct Binary Tree from Preorder and Inorder Traversal #110 Balanced Binary Tree
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