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Uber·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Apr 2026

Summary

Uber SWE interview with a tournament simulation problem that had two parts, the second of which was genuinely tricky. The construction part caught me off guard and I spent way too long on it.

Questions Asked (2)

Q1

You're given an array representing player ranks in a single-elimination tournament. Players are paired by adjacent indices each round, the stronger one (lower rank number) advances, and an unpaired last player gets a bye. Simulate the tournament and output the remaining players after each round.

Algorithms & Data Structures
Author's notes

Part one was fine, just iterate and pick the min of each adjacent pair, handle odd lengths by appending the last element.

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AI HintsAI Generated

Suggested Approach

Clarify the rules and edge cases, then simulate each round by iterating through the array in steps of two, comparing adjacent players and advancing the stronger (lower rank). Handle the odd-length case by carrying the last player forward as a bye. Repeat until one player remains, recording the array after each round.

Pro tip: Mention that you can optimize space by reusing the input array or using a queue, but prioritize clarity in the first pass. Also, explicitly state the time complexity: O(n) per round, O(n log n) overall, since the array halves each round.

1. Clarify requirements and edge cases

Ask about input size, whether ranks are unique, and how byes are handled. Confirm output format: list of arrays after each round.

2. Design the simulation loop

Iterate over rounds until one player remains. For each round, create a new list for winners and process pairs.

3. Process pairs and handle odd length

For i from 0 to length-2 step 2, compare arr[i] and arr[i+1], append the smaller. If length is odd, append the last element as a bye.

4. Record and repeat

After each round, add the current winners list to the result. Set the winners list as the new array and continue until length is 1.

5. Analyze complexity and test

State time complexity O(n log n) and space O(n). Walk through a small example to verify correctness.

Key Points to Mention

  • Simulation approach with iterative rounds
  • Handling odd number of players with a bye
  • Time and space complexity analysis
  • Edge cases: single player, even/odd lengths, duplicate ranks
  • Potential optimizations (e.g., in-place, queue) but trade-offs
  • Clear output format: list of arrays after each round

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.

Q2

Given n, construct an initial permutation of ranks 1 through n such that stronger players (lower rank numbers) are always eliminated in later rounds than weaker ones. The arrangement must work for any n, not just powers of two.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

This is where I got stuck for a while.

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AI HintsAI Generated

Suggested Approach

Model the tournament as a binary tree where each internal node represents a match and leaves are players. Assign ranks so that the depth of each player's leaf is non-increasing with rank (stronger players have deeper leaves). For non-powers of two, use byes or a balanced tree with dummy leaves to ensure the property holds.

Pro tip: Mention that the solution is essentially a 'seeding' problem and that byes should be given to the strongest players to maximize their potential rounds. This shows you understand real-world tournament design.

1. Understand the problem

Clarify that 'eliminated in later rounds' means stronger players must survive more rounds than weaker ones. The permutation is the initial ordering of players in the bracket.

2. Model as a binary tree

Represent the tournament as a full binary tree with n leaves (players). Each internal node is a match; the winner advances. The round of elimination is the depth of the leaf from the root.

3. Define the property

For ranks i < j (i stronger), the depth of leaf i must be >= depth of leaf j. So stronger players must be placed deeper in the tree.

4. Construct for powers of two

For n=2^k, a complete binary tree works. Assign ranks in order of increasing depth: rank 1 at deepest leaf, rank n at root's child (depth 1). This ensures stronger players last longer.

5. Extend to arbitrary n

For non-powers of two, add dummy leaves (byes) to make n' = next power of two. Assign byes to strongest players (they get a free pass). Then map ranks to leaves ensuring depth non-increasing with rank.

Key Points to Mention

  • Binary tree representation of tournament brackets
  • Depth of leaf corresponds to round of elimination
  • Monotonicity: stronger players must have greater or equal depth
  • Handling non-powers of two via byes or dummy leaves
  • Byes should be assigned to strongest players to maximize their rounds
  • Time and space complexity: O(n) to construct the permutation

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.