Interview Question 30: Longest increasing subsequence

Question

Explain and implement Longest increasing subsequence. Discuss time/space complexity and trade-offs.

What Interviewers Look For

  • Clear communication of approach before coding
  • Correct handling of edge cases
  • Clean, readable implementation
  • Awareness of alternatives

Approach

  1. Clarify inputs, outputs, and constraints
  2. Start with a brute-force solution if needed
  3. Optimize and discuss complexity
  4. Test with examples including edge cases
  // Skeleton — fill in during practice
function solution(input) {
  // O(n) typical for linear scans
  return input;
}

Follow-up Questions

  • How would this change at scale?
  • What breaks with concurrent access?
  • How would you test this thoroughly?