Problem database last updated: June 20, 2025
21 problems · 10 Easy, 9 Medium, 2 Hard · Ranked #87 of 458
10 Easy
48% · avg 23%
9 Medium
43% · avg 59%
2 Hard
10% · avg 18%
Based on 21 reported problems, ZScaler interviews are in line with industry averages - 10% Hard vs 18% overall.
Compared to the industry average, ZScaler puts unusual emphasis on trie (14.3% of problems, 5.4x the industry average), sliding-window (14.3% of problems, 3x the industry average), bit-manipulation (9.5% of problems, 2.8x the industry average). If you're short on time, these are the categories to double down on.
The most common topics are array (57.1%), hash-table (38.1%), string (23.8%), math (19%). Problems below are sorted by frequency, the ones at the top are asked most often.
| Problem | Difficulty | Frequency | Topics | |
|---|---|---|---|---|
Largest Number After Digit Swaps by Parity You are given a positive integer num. You may swap any two digits of num that have the same parity (i.e. both odd digits or both even digits). | Easy | Very Likely | sortingheap-priority-queue | Solve |
Apply Operations to Make Sum of Array Greater Than or Equal to k You are given a positive integer k. Initially, you have an array nums = [1]. | Medium | Very Likely | mathgreedyenumeration | Solve |
Maximum Strong Pair XOR II You are given a 0-indexed integer array nums. A pair of integers x and y is called a strong pair if it satisfies the condition: | Hard | Very Likely | arrayhash-tablebit-manipulation | Solve |
Maximum Strong Pair XOR I You are given a 0-indexed integer array nums. A pair of integers x and y is called a strong pair if it satisfies the condition: | Easy | Very Likely | arrayhash-tablebit-manipulation | Solve |
Day of the Year Given a string date representing a Gregorian calendar date formatted as YYYY-MM-DD, return the day number of the year. | Easy | Very Likely | mathstring | Solve |
Robot Bounded In Circle On an infinite plane, a robot initially stands at (0, 0) and faces north. Note that: | Medium | Very Likely | mathstringsimulation | Solve |
Rotate Image You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise). | Medium | Likely | arraymathmatrix | Solve |
Two Sum Given an array of integers nums and an integer target, return the indices of the two numbers that add up to target. | Easy | Likely | arrayhash-map | Solve |
Jump Game You are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your maximum jump length... | Medium | Likely | arraydynamic-programminggreedy | Solve |
Find the Smallest Divisor Given a Threshold Given an array of integers nums and an integer threshold, we will choose a positive integer divisor, divide all the array by it, and sum the division's result.... | Medium | Likely | arraybinary-search | Solve |
LRU Cache Design a data structure that follows the constraints of a Least Recently Used (LRU) cache. | Medium | Likely | hash-tablelinked-listdesign | Solve |
Linked List Cycle Given head, the head of a linked list, determine if the linked list has a cycle in it. | Easy | Likely | hash-tablelinked-listtwo-pointers | Solve |
Palindrome Linked List Given the head of a singly linked list, return true if it is a palindrome or false otherwise. | Easy | Likely | linked-listtwo-pointersstack | Solve |
Word Ladder A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that: | Hard | Likely | hash-tablestringbreadth-first-search | Solve |
Degree of an Array Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements. | Easy | Likely | arrayhash-table | Solve |
Minimum Increment to Make Array Unique You are given an integer array nums. In one move, you can pick an index i where 0 <= i < nums.length and increment nums[i] by 1. | Medium | Likely | arraygreedysorting | Solve |
Search in Rotated Sorted Array There is an integer array nums sorted in ascending order (with distinct values). | Medium | Likely | arraybinary-search | Solve |
Contains Duplicate Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct. | Easy | Likely | arrayhash-tablesorting | Solve |
Remove Duplicates from Sorted Array Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order o... | Easy | Likely | arraytwo-pointers | Solve |
Longest Common Prefix Write a function to find the longest common prefix string amongst an array of strings. | Easy | Likely | arraystringtrie | Solve |
Longest Substring Without Repeating Characters Given a string s, find the length of the longest substring without duplicate characters. | Medium | Likely | hash-tablestringsliding-window | Solve |
Largest Number After Digit Swaps by Parity
SolveYou are given a positive integer num. You may swap any two digits of num that have the same parity (i.e. both odd digits or both even digits).
Apply Operations to Make Sum of Array Greater Than or Equal to k
SolveYou are given a positive integer k. Initially, you have an array nums = [1].
Maximum Strong Pair XOR II
SolveYou are given a 0-indexed integer array nums. A pair of integers x and y is called a strong pair if it satisfies the condition:
Maximum Strong Pair XOR I
SolveYou are given a 0-indexed integer array nums. A pair of integers x and y is called a strong pair if it satisfies the condition:
Day of the Year
SolveGiven a string date representing a Gregorian calendar date formatted as YYYY-MM-DD, return the day number of the year.
Robot Bounded In Circle
SolveOn an infinite plane, a robot initially stands at (0, 0) and faces north. Note that:
Rotate Image
SolveYou are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).
Two Sum
SolveGiven an array of integers nums and an integer target, return the indices of the two numbers that add up to target.
Jump Game
SolveYou are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your maximum jump length...
Find the Smallest Divisor Given a Threshold
SolveGiven an array of integers nums and an integer threshold, we will choose a positive integer divisor, divide all the array by it, and sum the division's result....
LRU Cache
SolveDesign a data structure that follows the constraints of a Least Recently Used (LRU) cache.
Linked List Cycle
SolveGiven head, the head of a linked list, determine if the linked list has a cycle in it.
Palindrome Linked List
SolveGiven the head of a singly linked list, return true if it is a palindrome or false otherwise.
Word Ladder
SolveA transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that:
Degree of an Array
SolveGiven a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements.
Minimum Increment to Make Array Unique
SolveYou are given an integer array nums. In one move, you can pick an index i where 0 <= i < nums.length and increment nums[i] by 1.
Search in Rotated Sorted Array
SolveThere is an integer array nums sorted in ascending order (with distinct values).
Contains Duplicate
SolveGiven an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.
Remove Duplicates from Sorted Array
SolveGiven an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order o...
Longest Common Prefix
SolveWrite a function to find the longest common prefix string amongst an array of strings.
Longest Substring Without Repeating Characters
SolveGiven a string s, find the length of the longest substring without duplicate characters.
Frequency scores are based on crowdsourced interview reports. A higher score means the problem has been reported more often in recent ZScaler interviews.
Very Likely
75-100%
Likely
50-74%
Sometimes
25-49%
Rare
0-24%
ZScaler interviews focus heavily on array, hash-table, string 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. ZScaler 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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ZScaler has been reported to ask 21 distinct coding problems. The most common topics are array, hash-table, string. 10 are Easy difficulty, 9 are Medium, and 2 are Hard. Problems are sorted by frequency - the ones at the top are asked most often.
Based on 21 reported problems, ZScaler interviews are in line with industry averages - 10% Hard vs 18% overall. 43% 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, hash-table, string. 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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