Sigmoid coding interview
questions, leaked.
6 problems reported across recent Sigmoid interviews. Top patterns: array, sorting, prefix sum. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Sigmoid's interview is 6 problems deep, and they're not messing around. Five mediums and one hard, with array patterns dominating the ask. You're looking at sorting, prefix sums, two-pointer logic, and tree traversal woven through most of their assessment. The depth is real, but the set is small enough to predict. If you hit the wall on a prefix-sum problem or freeze on the greedy sort in a linked-list reversal, StealthCoder runs invisible during the live OA and surfaces a working solution in seconds.
Top problems at Sigmoid
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Boats to Save People | MEDIUM | 100.0 | 60% | Array · Two Pointers · Greedy |
| 02 | Binary Tree Zigzag Level Order Traversal | MEDIUM | 100.0 | 62% | Tree · Breadth-First Search · Binary Tree |
| 03 | Product of Array Except Self | MEDIUM | 100.0 | 68% | Array · Prefix Sum |
| 04 | Group Anagrams | MEDIUM | 100.0 | 71% | Array · Hash Table · String |
| 05 | Reverse Nodes in k-Group | HARD | 100.0 | 63% | Linked List · Recursion |
| 06 | Max Consecutive Ones III | MEDIUM | 100.0 | 66% | Array · Binary Search · Sliding Window |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual Sigmoid OA. The proctor cannot see it. Screen share cannot detect it. Made by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too.
Get StealthCoder- array4 · 67%
- sorting2 · 33%
- prefix sum2 · 33%
- two pointers1 · 17%
- greedy1 · 17%
- tree1 · 17%
- breadth first search1 · 17%
- binary tree1 · 17%
- hash table1 · 17%
- string1 · 17%
Arrays appear in 4 out of 6 problems, so that's your north star. Sorting shows up twice, prefix sums twice. Boats to Save People and Max Consecutive Ones III both hinge on sorting and prefix-sum logic applied to constraints. Product of Array Except Self and Group Anagrams lean hash table and sorting too. Binary Tree Zigzag Level Order Traversal and Reverse Nodes in k-Group are the pattern breaks, but they're both textbook medium-to-hard patterns you've seen before. The real risk is mixing array intuition with greedy choice or BFS on the tree walk. That's where StealthCoder becomes your safety net if you blank mid-assessment. Drill arrays and sorting first. Tree traversal and linked-list recursion are secondary.
Companies with similar patterns
If you prepped for Sigmoid, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Sigmoid.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen and surfaces a working solution in under 2 seconds. Made by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Sigmoid interview FAQ
Should I prioritize array problems before anything else for Sigmoid?+
Yes. Arrays appear in 4 of 6 problems, often combined with sorting or prefix-sum logic. Boats to Save People, Product of Array Except Self, Group Anagrams, and Max Consecutive Ones III all require array fluency. Master these four before you touch the linked-list or tree problems.
How much time should I spend on prefix-sum techniques?+
Prefix sums show up twice in their assessment (Product of Array Except Self and Max Consecutive Ones III). If you're not rock-solid on building and querying prefix arrays in O(n) time, practice this pattern for at least 2 to 3 hours before your OA.
Is the hard problem (Reverse Nodes in k-Group) a deal-breaker?+
Not if you're solid on recursion and linked-list pointers. It's one of six. The five mediums are weighted heavier. Know recursion and list reversal in place, but don't let the hard problem consume your prep time. It's your 10% hedge, not your 90%.
Do I need to study trees and BFS separately?+
Binary Tree Zigzag Level Order Traversal is their only tree problem. Yes, you need BFS and level-order logic, but it's one of six. Get array and sorting solid first, then spend 60 to 90 minutes on tree traversal and zigzag patterns.
What's the biggest gap most candidates hit on Sigmoid's assessment?+
Mixing greedy logic with sorting (Boats to Save People). Candidates know how to sort, but they freeze on the greedy choice of pairing lightest and heaviest people. Drill the greedy reasoning, not just the sort. This is where live panic sets in.