Count longest subsequence in binary tree
Last updated: March 23, 2026
Quick Overview
Given a binary tree, write a function to count the length of the longest subsequence that follows the properties of a binary tree. A subsequence is defined as a sequence derived from the tree by deleting some or no nodes without changing the order of the remaining nodes. The function should return an integer representing the length of this longest subsequence.
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March 23, 2026523
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Given a binary tree, write a function to count the length of the longest subsequence that follows the properties of a binary tree. A subsequence is defined as a sequence derived from the tree by deleting some or no nodes without changing the order of the remaining nodes. The function should return an integer representing the length of this longest subsequence.
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to find the length of the longest subsequence in a binary tree. A subsequence is formed by deleting nodes while maintaining the order of the remaining nodes. The properties of ...
Approach
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Recursive DFS Function: We will define a recursive function that takes a node as an argument and returns the length of the longest subsequence from that node.
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Base Case: If the current ...
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