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Meta·Software Engineer·Onsite - Coding / Algorithms·Intermediate

Intermediate
May 2026

Summary

Meta SWE coding round, one algorithmic problem about splitting an array into two parts with equal sum. Pretty lean on detail but the problem itself is a classic that can go in a few different directions depending on constraints.

Questions Asked (1)

Q1

Given an array of integers, partition it into two sub-arrays such that both have equal sums.

Algorithms & Data Structures
Author's notes

My first instinct was prefix sums and I think that's the right move.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem constraints and define what 'partition' means (e.g., contiguous subarrays or subsets). Then, reduce the problem to finding a subset with sum equal to half the total sum, and discuss algorithmic approaches like dynamic programming or greedy with sorting, analyzing time and space complexity.

Pro tip: Always check if the total sum is odd; if so, equal partition is impossible. Also, mention that for contiguous subarrays, a linear-time prefix sum approach works, but for arbitrary subsets, it's NP-complete (subset sum), so discuss trade-offs.

1. Clarify the problem

Ask whether the partition must be into contiguous subarrays or arbitrary subsets, and whether the subarrays must cover the entire array. Also confirm if elements can be negative.

2. Check feasibility

Compute the total sum. If it's odd, return false immediately. Otherwise, the target sum for each partition is total_sum / 2.

3. Choose an approach

For contiguous subarrays, use prefix sums to find a split point in O(n). For arbitrary subsets, use dynamic programming (subset sum) with O(n * target) time and O(target) space, or meet-in-the-middle for large n.

4. Implement and optimize

Write clean code for the chosen approach, handle edge cases (empty array, single element, zeros), and discuss potential optimizations like early termination or bitset DP.

5. Analyze complexity

State time and space complexity, and discuss trade-offs between approaches, especially if the problem is NP-complete for arbitrary subsets.

Key Points to Mention

  • Total sum must be even; otherwise, impossible.
  • Reduction to subset sum problem for arbitrary subsets.
  • Dynamic programming approach with boolean array or bitset.
  • Prefix sum approach for contiguous subarrays.
  • Handling negative numbers and zeros.
  • Time and space complexity analysis (e.g., O(n * sum) for DP).

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