Problem database last updated: June 20, 2025
25 problems · 10 Easy, 11 Medium, 4 Hard · Ranked #79 of 458
10 Easy
40% · avg 23%
11 Medium
44% · avg 59%
4 Hard
16% · avg 18%
Based on 25 reported problems, Siemens interviews are in line with industry averages - 16% Hard vs 18% overall.
Compared to the industry average, Siemens puts unusual emphasis on binary-indexed-tree (8% of problems, 18x the industry average), segment-tree (8% of problems, 13.1x the industry average), linked-list (20% 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 (56%), sorting (32%), string (24%), hash-table (24%). Problems below are sorted by frequency, the ones at the top are asked most often.
| Problem | Difficulty | Frequency | Topics | |
|---|---|---|---|---|
Peaks in Array A peak in an array arr is an element that is greater than its previous and next element in arr. | Hard | Very Likely | arraybinary-indexed-treesegment-tree | Solve |
Minimized Maximum of Products Distributed to Any Store You are given an integer n indicating there are n specialty retail stores. There are m product types of varying amounts, which are given as a 0-indexed integer... | Medium | Very Likely | arraybinary-searchgreedy | 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 |
Valid Parentheses Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. | Easy | Very Likely | stringstack | Solve |
Merge Intervals Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cove... | Medium | Very Likely | arraysorting | Solve |
Letter Combinations of a Phone Number Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order. | Medium | Likely | hash-tablestringbacktracking | Solve |
Best Time to Buy and Sell Stock You are given an array prices where prices[i] is the price of a given stock on the ith day. | Easy | Likely | arraydynamic-programming | Solve |
Reverse Linked List Given the head of a singly linked list, reverse the list, and return the reversed list. | Easy | Likely | linked-listrecursion | 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 |
Merge Two Sorted Lists You are given the heads of two sorted linked lists list1 and list2. | Easy | Likely | linked-listrecursion | Solve |
LFU Cache Design and implement a data structure for a Least Frequently Used (LFU) cache. | Hard | Likely | hash-tablelinked-listdesign | Solve |
The Skyline Problem A city's skyline is the outer contour of the silhouette formed by all the buildings in that city when viewed from a distance. Given the locations and heights of... | Hard | Likely | arraydivide-and-conquerbinary-indexed-tree | 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 |
First Missing Positive Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums. | Hard | Likely | arrayhash-table | Solve |
Rotate List Given the head of a linked list, rotate the list to the right by k places. | Medium | Likely | linked-listtwo-pointers | Solve |
Valid Anagram Given two strings s and t, return true if t is an anagram of s, and false otherwise. | Easy | Likely | hash-tablestringsorting | 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 |
Largest Number Given a list of non-negative integers nums, arrange them such that they form the largest number and return it. | Medium | Likely | arraystringgreedy | Solve |
3Sum Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0. | Medium | Likely | arraytwo-pointerssorting | Solve |
Seat Reservation Manager Design a system that manages the reservation state of n seats that are numbered from 1 to n. | Medium | Likely | designheap-priority-queue | 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 |
Angle Between Hands of a Clock Given two numbers, hour and minutes, return the smaller angle (in degrees) formed between the hour and the minute hand. | Medium | Likely | math | Solve |
Maximum Product of Three Numbers Given an integer array nums, find three numbers whose product is maximum and return the maximum product. | Easy | Likely | arraymathsorting | Solve |
Group Anagrams Given an array of strings strs, group the anagrams together. You can return the answer in any order. | Medium | Likely | arrayhash-tablestring | Solve |
Minimum Add to Make Parentheses Valid A parentheses string is valid if and only if: | Medium | Likely | stringstackgreedy | Solve |
Peaks in Array
SolveA peak in an array arr is an element that is greater than its previous and next element in arr.
Minimized Maximum of Products Distributed to Any Store
SolveYou are given an integer n indicating there are n specialty retail stores. There are m product types of varying amounts, which are given as a 0-indexed integer...
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.
Valid Parentheses
SolveGiven a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
Merge Intervals
SolveGiven an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cove...
Letter Combinations of a Phone Number
SolveGiven a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.
Best Time to Buy and Sell Stock
SolveYou are given an array prices where prices[i] is the price of a given stock on the ith day.
Reverse Linked List
SolveGiven the head of a singly linked list, reverse the list, and return the reversed list.
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.
Merge Two Sorted Lists
SolveYou are given the heads of two sorted linked lists list1 and list2.
LFU Cache
SolveDesign and implement a data structure for a Least Frequently Used (LFU) cache.
The Skyline Problem
SolveA city's skyline is the outer contour of the silhouette formed by all the buildings in that city when viewed from a distance. Given the locations and heights of...
Two Sum
SolveGiven an array of integers nums and an integer target, return the indices of the two numbers that add up to target.
First Missing Positive
SolveGiven an unsorted integer array nums. Return the smallest positive integer that is not present in nums.
Rotate List
SolveGiven the head of a linked list, rotate the list to the right by k places.
Valid Anagram
SolveGiven two strings s and t, return true if t is an anagram of s, and false otherwise.
Palindrome Linked List
SolveGiven the head of a singly linked list, return true if it is a palindrome or false otherwise.
Largest Number
SolveGiven a list of non-negative integers nums, arrange them such that they form the largest number and return it.
3Sum
SolveGiven an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.
Seat Reservation Manager
SolveDesign a system that manages the reservation state of n seats that are numbered from 1 to n.
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...
Angle Between Hands of a Clock
SolveGiven two numbers, hour and minutes, return the smaller angle (in degrees) formed between the hour and the minute hand.
Maximum Product of Three Numbers
SolveGiven an integer array nums, find three numbers whose product is maximum and return the maximum product.
Group Anagrams
SolveGiven an array of strings strs, group the anagrams together. You can return the answer in any order.
Minimum Add to Make Parentheses Valid
SolveA parentheses string is valid if and only if:
Frequency scores are based on crowdsourced interview reports. A higher score means the problem has been reported more often in recent Siemens interviews.
Very Likely
75-100%
Likely
50-74%
Sometimes
25-49%
Rare
0-24%
Siemens interviews focus heavily on array, sorting, 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. Siemens 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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Siemens has been reported to ask 25 distinct coding problems. The most common topics are array, sorting, string. 10 are Easy difficulty, 11 are Medium, and 4 are Hard. Problems are sorted by frequency - the ones at the top are asked most often.
Based on 25 reported problems, Siemens interviews are in line with industry averages - 16% Hard vs 18% overall. 44% 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, sorting, 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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