Practice/Meta/Leetcode 199. Binary Tree Right Side View

Leetcode 199. Binary Tree Right Side View

CodingMust

Problem

Imagine standing to the right of a binary tree and looking at it from that perspective. You can only see certain nodes — specifically, the rightmost node at each level of the tree.

Given the root of a binary tree, return a list of the values of the nodes you can see when viewing the tree from its right side. The values should be ordered from top to bottom, corresponding to each level of the tree.

Requirements

1. Return the rightmost node value at each depth level
2. Values must be ordered from the root level down to the deepest visible level
3. Handle edge cases including empty trees and single-node trees
4. If a level has only left children, those nodes should still be included as they are the "rightmost" at that depth

Constraints

• The number of nodes in the tree is in the range [0, 100]
• Node values are in the range [-100, 100]
• Expected time complexity: O(n) where n is the number of nodes
• Expected space complexity: O(h) where h is the height of the tree (for recursive approach) or O(w) where w is the maximum width (for iterative approach)

Examples

Example 1:

` Input: root = [1, 2, 3, null, 5, null, 4] Tree structure: 1 /
2 3 \
5 4

Output: [1, 3, 4] Explanation: Looking from the right side:

• At depth 0, we see node 1
• At depth 1, we see node 3 (rightmost)
• At depth 2, we see node 4 (rightmost) `

Example 2:

` Input: root = [1, 2, null, 3] Tree structure: 1 / 2 / 3

Output: [1, 2, 3] Explanation: Even though all nodes are on the left branch, each is the rightmost (and only) node at its level `

Example 3:

Input: root = [] Output: [] Explanation: An empty tree has no visible nodes