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Longest Strictly Increasing Subsequence Coding / DSA Interview

Given a sequence of integers, find the length of the longest subsequence (not necessarily contiguous) whose elements are strictly increasing.

Practice in Interview Dashboard

1. Problem Statement

You are given a sequence of integers. Find the length of the longest subsequence, not necessarily contiguous, whose elements are strictly increasing.

2. Live Coding Format

Work in the provided coding workspace while explaining your decisions to the live interviewer. Validation may use inline tests, examples, comments, or a verbal walkthrough.

3. Key Focus Areas

  • 1
    Problem clarification and contract
  • 2
    Approach exploration and optimality
  • 3
    Think-aloud communication and pacing
  • 4
    Implementation correctness
  • 5
    Code quality and language fluency
  • 6
    Handwritten tests and dry run
  • 7
    Debugging and self-correction
  • 8
    Complexity analysis
  • 9
    Follow-up performance

4. What Strong Candidates Should Demonstrate

  • ✓Clarify strictness of the ordering and behavior on empty or fully non-increasing input before coding.
  • ✓Explain an O(n^2) DP baseline and improve to an O(n log n) patience-sorting approach.
  • ✓Think aloud while implementing careful DP or binary-search-based tail tracking.
  • ✓Validate with explicit expected outputs and a top-to-bottom handwritten dry run.
  • ✓Analyze time and space complexity and handle a bounded follow-up modification.

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Practice this problem in the live coding workspace while the interviewer probes your clarification, implementation, trade-offs, and validation.

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Core Concepts

Dynamic ProgrammingBinary SearchArraysComplexity Analysis

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