sunrise·Software Engineer·Onsite - Coding / Algorithms
Jun 2026
Coding round at Sunrise for a software engineer role, heavy on classic algorithm and puzzle questions. Eight problems across linked lists, grids, sorting, and logic puzzles. No behavioral stuff at all, just back-to-back technical problems.
- Reverse a singly linked list iteratively and/or recursively, returning the new head.
- Given coordinates (x, y) on an infinite 2D grid filled by a counterclockwise outward square spiral starting at 1, compute the value at that cell in O(1) time without simulating the spiral.
- 100 bulbs are all off. Person k toggles every bulb that is a multiple of k. Which bulbs are on after all 100 people go?
- Given only a pointer to a node inside a singly linked list (no head pointer), delete that node from the list in O(1) time.
- Four people with crossing times 1, 2, 5, and 6 minutes need to cross a bridge using one torch. At most two cross at a time and the pair moves at the slower person's pace. Find a schedule under 13 minutes.
- Given the root of a binary tree, determine whether it is a valid binary search tree.
- Given a list of intervals, merge all overlapping ones and return the result.
- Given an unsorted array, find the maximum difference between adjacent elements in the sorted version. Can you do better than O(n log n)?
“Classic warmup.” The rest of the author's notes on Software Engineer interview at sunrise, Onsite - Coding / Algorithms round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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