Problem database last updated: June 20, 2025
17 problems · 5 Easy, 8 Medium, 4 Hard · Ranked #104 of 458
5 Easy
29% · avg 23%
8 Medium
47% · avg 59%
4 Hard
24% · avg 18%
Based on 17 reported problems, Zenefits interviews are slightly harder than average - 24% Hard vs 18% across all companies.
Compared to the industry average, Zenefits puts unusual emphasis on topological-sort (11.8% of problems, 10x the industry average), divide-and-conquer (17.6% of problems, 4.3x the industry average), graph (11.8% of problems, 4x the industry average). If you're short on time, these are the categories to double down on.
The most common topics are array (35.3%), string (23.5%), hash-table (17.6%), divide-and-conquer (17.6%). Problems below are sorted by frequency, the ones at the top are asked most often.
| Problem | Difficulty | Frequency | Topics | |
|---|---|---|---|---|
Majority Element Given an array nums of size n, return the majority element. | Easy | Very Likely | arrayhash-tabledivide-and-conquer | Solve |
Valid Parentheses Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. | Easy | Very Likely | stringstack | Solve |
Valid Palindrome A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forwa... | Easy | Very Likely | two-pointersstring | Solve |
Reverse Linked List Given the head of a singly linked list, reverse the list, and return the reversed list. | Easy | Very Likely | linked-listrecursion | Solve |
Majority Element II Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. | Medium | Very Likely | arrayhash-tablesorting | Solve |
Excel Sheet Column Title Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet. | Easy | Very Likely | mathstring | Solve |
Median of Two Sorted Arrays Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays. | Hard | Very Likely | arraybinary-searchdivide-and-conquer | Solve |
Trapping Rain Water Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining. | Hard | Very Likely | arraytwo-pointersdynamic-programming | Solve |
Generate Parentheses Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. | Medium | Very Likely | stringdynamic-programmingbacktracking | Solve |
Number of Islands Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands. | Medium | Very Likely | arraydepth-first-searchbreadth-first-search | Solve |
N-Queens II The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other. | Hard | Very Likely | backtracking | Solve |
Course Schedule There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, b... | Medium | Very Likely | depth-first-searchbreadth-first-searchgraph | Solve |
Course Schedule II There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, b... | Medium | Very Likely | depth-first-searchbreadth-first-searchgraph | Solve |
LRU Cache Design a data structure that follows the constraints of a Least Recently Used (LRU) cache. | Medium | Very Likely | hash-tablelinked-listdesign | Solve |
Sliding Window Maximum You are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see... | Hard | Very Likely | arrayqueuesliding-window | Solve |
Min Stack Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. | Medium | Very Likely | stackdesign | Solve |
Convert Sorted List to Binary Search Tree Given the head of a singly linked list where elements are sorted in ascending order, convert it to a height-balanced binary search tree. | Medium | Very Likely | linked-listdivide-and-conquertree | Solve |
Majority Element
SolveGiven an array nums of size n, return the majority element.
Valid Parentheses
SolveGiven a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
Valid Palindrome
SolveA phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forwa...
Reverse Linked List
SolveGiven the head of a singly linked list, reverse the list, and return the reversed list.
Majority Element II
SolveGiven an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times.
Excel Sheet Column Title
SolveGiven an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.
Median of Two Sorted Arrays
SolveGiven two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays.
Trapping Rain Water
SolveGiven n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.
Generate Parentheses
SolveGiven n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
Number of Islands
SolveGiven an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.
N-Queens II
SolveThe n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other.
Course Schedule
SolveThere are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, b...
Course Schedule II
SolveThere are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, b...
LRU Cache
SolveDesign a data structure that follows the constraints of a Least Recently Used (LRU) cache.
Sliding Window Maximum
SolveYou are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see...
Min Stack
SolveDesign a stack that supports push, pop, top, and retrieving the minimum element in constant time.
Convert Sorted List to Binary Search Tree
SolveGiven the head of a singly linked list where elements are sorted in ascending order, convert it to a height-balanced binary search tree.
Frequency scores are based on crowdsourced interview reports. A higher score means the problem has been reported more often in recent Zenefits interviews.
Very Likely
75-100%
Likely
50-74%
Sometimes
25-49%
Rare
0-24%
Zenefits interviews focus heavily on array, string, hash-table 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. Zenefits 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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Zenefits has been reported to ask 17 distinct coding problems. The most common topics are array, string, hash-table. 5 are Easy difficulty, 8 are Medium, and 4 are Hard. Problems are sorted by frequency - the ones at the top are asked most often.
Based on 17 reported problems, Zenefits interviews are slightly harder than average - 24% Hard vs 18% across all companies. 47% 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, string, hash-table. Practice solving them under time pressure and explaining your approach out loud. Mock interviews with AI can simulate the real experience.
Simulate a real Zenefits coding interview with an AI interviewer. Get a scorecard with specific feedback on your problem-solving, code quality, and communication.
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