Problem database last updated: June 20, 2025
6 problems · 0 Easy, 5 Medium, 1 Hard · Ranked #217 of 458
0 Easy
0% · avg 23%
5 Medium
83% · avg 59%
1 Hard
17% · avg 18%
Based on 6 reported problems, Sigmoid interviews are in line with industry averages - 17% Hard vs 18% overall. The majority (83%) of questions are Medium difficulty, which is typical for companies that want to see solid fundamentals without excessive trick questions.
Compared to the industry average, Sigmoid puts unusual emphasis on prefix-sum (33.3% of problems, 10x the industry average), sorting (33.3% of problems, 2.3x the industry average). If you're short on time, these are the categories to double down on.
The most common topics are array (66.7%), prefix-sum (33.3%), sorting (33.3%), hash-table (16.7%). Problems below are sorted by frequency, the ones at the top are asked most often.
| Problem | Difficulty | Frequency | Topics | |
|---|---|---|---|---|
Product of Array Except Self Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i]. | Medium | Very Likely | arrayprefix-sum | Solve |
Group Anagrams Given an array of strings strs, group the anagrams together. You can return the answer in any order. | Medium | Very Likely | arrayhash-tablestring | Solve |
Reverse Nodes in k-Group Given the head of a linked list, reverse the nodes of the list k at a time, and return the modified list. | Hard | Very Likely | linked-listrecursion | Solve |
Binary Tree Zigzag Level Order Traversal Given the root of a binary tree, return the zigzag level order traversal of its nodes' values. (i.e., from left to right, then right to left for the next level... | Medium | Very Likely | treebreadth-first-searchbinary-tree | Solve |
Boats to Save People You are given an array people where people[i] is the weight of the ith person, and an infinite number of boats where each boat can carry a maximum weight of lim... | Medium | Very Likely | arraytwo-pointersgreedy | Solve |
Max Consecutive Ones III Given a binary array nums and an integer k, return the maximum number of consecutive 1's in the array if you can flip at most k 0's. | Medium | Very Likely | arraybinary-searchsliding-window | Solve |
Product of Array Except Self
SolveGiven an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i].
Group Anagrams
SolveGiven an array of strings strs, group the anagrams together. You can return the answer in any order.
Reverse Nodes in k-Group
SolveGiven the head of a linked list, reverse the nodes of the list k at a time, and return the modified list.
Binary Tree Zigzag Level Order Traversal
SolveGiven the root of a binary tree, return the zigzag level order traversal of its nodes' values. (i.e., from left to right, then right to left for the next level...
Boats to Save People
SolveYou are given an array people where people[i] is the weight of the ith person, and an infinite number of boats where each boat can carry a maximum weight of lim...
Max Consecutive Ones III
SolveGiven a binary array nums and an integer k, return the maximum number of consecutive 1's in the array if you can flip at most k 0's.
Frequency scores are based on crowdsourced interview reports. A higher score means the problem has been reported more often in recent Sigmoid interviews.
Very Likely
75-100%
Likely
50-74%
Sometimes
25-49%
Rare
0-24%
Sigmoid interviews focus heavily on array, prefix-sum, sorting problems. If you're short on time, these are the categories to prioritize. The problems on this page are sorted by frequency, so start from the top and work your way down.
Beyond solving problems, practice explaining your approach. Sigmoid interviewers care about your thought process - how you break down a problem, consider edge cases, and evaluate tradeoffs between solutions. A clean O(n) solution you can explain clearly beats an O(log n) solution you can't articulate.
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Sigmoid has been reported to ask 6 distinct coding problems. The most common topics are array, prefix-sum, sorting. 0 are Easy difficulty, 5 are Medium, and 1 are Hard. Problems are sorted by frequency - the ones at the top are asked most often.
Based on 6 reported problems, Sigmoid interviews are in line with industry averages - 17% Hard vs 18% overall. 83% of questions are Medium difficulty. Focus on the high-frequency Medium problems first, then work through the Hard ones.
Start with the highest-frequency problems listed on this page. Focus on the core topics: array, prefix-sum, sorting. Practice solving them under time pressure and explaining your approach out loud. Mock interviews with AI can simulate the real experience.
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