‹ DS&A interview · Socratic
DSA · Arrays & Dynamic Programming · #114

Maximum Sum Circular Subarray

Module 75 · difficulty 3/5·⏱ 30:00starts on first keystroke

Given a **circular** integer array `nums` of length `n`, return the maximum possible sum of a non-empty subarray. A circular array means the end connects to the beginning: the element after `nums[n-1]` is `nums[0]`. A subarray may wrap around the end, but it may include each element **at most once** (its length is at most `n`). Implement `function maxSubarraySumCircular(nums)` returning the maximum subarray sum.

Examples
  • nums = [1,-2,3,-2] → 3 — Subarray [3] has the largest sum 3.
  • nums = [5,-3,5] → 10 — Subarray [5,5] wraps around: nums[2] + nums[0] = 10.
  • nums = [-3,-2,-3] → -2 — All negative; the best single element is -2.
Constraints
  • · n == nums.length
  • · 1 <= n <= 3 * 10^4
  • · -3 * 10^4 <= nums[i] <= 3 * 10^4
Session phases
A · Clarify
B · Approach
C · Complexity
D · Edges
E · Code
F · Tradeoff
G · Score
Phase A — Clarify
Ask questions about input bounds, types, and edge constraints.
Ask the coach clarifying questions about the problem.
When you've covered this phase, advance to the next.