Count longest subsequence in array
Last updated: February 14, 2026
Quick Overview
Count the number of longest subsequence in the given array.
Salesforce
Coding & Algorithms
Software Engineer
Salesforce
February 14, 2026Software Engineer
Onsite
Coding & Algorithms
Hard
125
5
1,477 solved
Count the number of longest subsequence in the given array.
Salesforce uses this problem in the Onsite to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
Key Topics to Cover
Graph algorithms and traversal
Dynamic programming and memoization
Common algorithm patterns (sliding window, two pointers, BFS/DFS)
Data structure selection and trade-offs
Hash maps and frequency counting
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.
Possible Follow-up Questions
- How would you test this solution thoroughly?
- How would your solution change if the input was sorted?
- How would you parallelize this solution?
- Can you optimize the space complexity of your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to count the number of longest increasing subsequences (LIS) in a given array. This problem can be approached using dynamic programming (DP) combined with a frequency counting ...
Approach
- Initialization: Create two arrays,
lengthsandcounts, both of the same length as the input array. Initializelengths[i]to 1 (each element is an LIS of length 1), andcounts[i]to 1 (t...
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