Is Binary Tree Longest Consecutive Sequence easy or hard?

Binary Tree Longest Consecutive Sequence is generally classified as a medium-level problem. The traversal itself is straightforward, but recognizing that the sequence length should propagate through recursion is the key insight.

Binary Tree Longest Consecutive Sequence Python/Java solution

Most implementations perform a recursive DFS function that receives the current node, parent value, and running length. The same logic works across Python, Java, C++, Go, and TypeScript because it only requires tree traversal and integer comparisons.

How to solve Binary Tree Longest Consecutive Sequence in O(n)?

Perform a DFS while passing the parent value and the current sequence length. If the current node equals parent + 1, increase the length; otherwise reset it to 1. Update a global maximum during traversal. Because each node is visited once, the algorithm runs in O(n) time.

What is the best approach for Binary Tree Longest Consecutive Sequence?

The best approach is a single depth-first search that tracks the parent value and current consecutive length. During traversal, compare the current node with its parent and extend the sequence if the value increases by one. This method visits each node once, giving O(n) time complexity and O(h) recursion space.

Is Binary Tree Longest Consecutive Sequence asked at Google/Amazon/Meta?

Binary tree traversal problems like this frequently appear in interviews at companies such as Google, Amazon, and Meta. Variations involving consecutive paths, longest paths, or value constraints are common during tree and DFS interview rounds.

What data structure is used in Binary Tree Longest Consecutive Sequence?

The problem uses a binary tree as the primary data structure and is typically solved using depth-first search recursion. The recursion stack implicitly stores traversal state such as parent value and current sequence length.

What is the time complexity of Binary Tree Longest Consecutive Sequence?

The optimal DFS solution runs in O(n) time because each node in the binary tree is processed exactly once. The recursion stack uses O(h) space where h is the height of the tree. A brute-force approach that starts a DFS from every node can degrade to O(n^2) time.

298. Binary Tree Longest Consecutive Sequence - Practice Online

Given the root of a binary tree, return the length of the longest consecutive sequence path.

A consecutive sequence path is a path where the values increase by one along the path.

Note that the path can start at any node in the tree, and you cannot go from a node to its parent in the path.

Example 1:

Input: root = [1,null,3,2,4,null,null,null,5]
Output: 3
Explanation: Longest consecutive sequence path is 3-4-5, so return 3.

Example 2:

Input: root = [2,null,3,2,null,1]
Output: 2
Explanation: Longest consecutive sequence path is 2-3, not 3-2-1, so return 2.

Constraints:

The number of nodes in the tree is in the range [1, 3 * 10⁴].
-3 * 10⁴ <= Node.val <= 3 * 10⁴