Top 26 coding questions to crack the Microsoft interview

Aiming for a career at Microsoft is a worthy challenge given the company’s excellent track record for technological innovation, generous compensation packages, and flexible work-life balance.

As the largest and arguably most influential software company in the world, prospective applicants may find the technical interview process daunting. However, familiarizing yourself with the type of technical questions that will be presented to you and learning to recognize coding patterns will help you navigate these interviews with greater confidence.

We’ll start with an introduction to 26 common coding questions, move on to an overview of the complete interview process for software engineers, move on to frequently asked technical questions, and then wrap up with additional guidance and resources to maximize your chances of receiving an offer.

Topics covered:

• 26 common coding questions
• Overview of the Microsoft hiring process
• How to prepare for the interview
• Wrapping up and next steps

26 common coding questions

As you go over each question, get into the habit of diagramming the problem before jumping straight to writing code. Breaking down a problem first gives you a chance to ask questions and get any important information you need to come up with the best possible solution. Take a moment to explain your thought process to yourself as if you were the interviewer.

Take some time to reflect on the efficiency of your solution, and try to see if you can make your answer more elegant by simplifying it.

Lastly, always remember to validate your solutions.

Alright, let’s dive in!

Arrays

1. Find the missing number in a given array

Problem Statement: Given an array of positive numbers ranging from 1 to n, such that all numbers from 1 to n are present except one number x, find x. Assume the input array is unsorted.

2. Determine if the sum of two integers is equal to a given value

Problem Statement: Given an array of integers and a value, determine if there are any two integers in the array whose sum is equal to the given value. Return true if the sum exists, and false if it does not. Consider the following array and its target sums:

3. Set columns and rows as zeroes

Problem Statement: Given a two-dimensional array, if any element within is zero, make its whole row and column zero. Consider the matrix below.

There are two zeros in the input matrix at positions (1,1) and (2,3). The output of this should be a matrix in which the first and second rows become zero and the first and third columns become zero. Below is the expected output matrix.

Linked Lists

4. Add two integers

Problem Statement: Given the head pointers of two linked lists where each linked list represents an integer number (each node is a digit), add them and return the resulting linked list. In the example below, the first node in a list represents the least significant digit.

5. Copy linked list with arbitrary pointer

Problem Statement: You are given a linked list where the node has two pointers. The first is the regular next pointer. The second pointer is called arbitrary_pointer and it can point to any node in the linked list.

Here, deep copy means that any operations on the original list (inserting, modifying, and removing) should not affect the copied list.

Here’s an example of a linked list with arbitrary pointers connected.

6. Merge two sorted linked lists

Problem Statement: Write a function that takes two sorted linked lists and merges them. The function should return a single, sorted list made from splicing the nodes of the first two lists together.

For example, if the first linked list is 1 -> 2 -> 4 and the second linked list is 3 -> 5 -> 6, then the output would be 1 -> 2 -> 3 -> 4 -> 5 -> 6

Trees

7. Level order traversal of binary tree

Problem Statement: Given the root of a binary tree, display the node values at each level.

The level order traversal for this binary tree looks like this:

100
50, 20
25, 75, 350

8. Connect all siblings

Problem Statement: Connect the sibling pointer to the next node in the same level. The last node in each level should point to the first node of the next level in the tree.

9. Check a given binary tree for symmetry

Problem Statement: Given a binary tree, write a program that will return true if the binary tree is a mirror image of itself, and false if it is not.

The correct output given this binary tree would be true because it is symmetrical.

Strings

10. Reverse words in a sentence

Problem Statement: Reverse the order of words in a given sentence.

Example: "sphinx of black quartz judge my vow" should output as "vow my judge quartz black of sphinx"

11. Find all palindrome substrings

Problem Statement: Given a string, find all non-single letter substrings that are palindromes.

Example:

An string input of "poppopo" would return "pop", "opo", "oppo", and "poppop".

12. String segmentation

Problem Statement: Given a dictionary of words and a large input string, find whether or not the input string can be completely segmented into the words of that dictionary.

Dynamic Programming

13. Find the maximum single sell profit

Problem Statement: Given a list of daily stock prices (integers for simplicity), return the buy and sell prices that will maximize the single buy/sell profit. If you can’t make any profit, try to minimize the loss.

For the below examples, buy (orange) and sell (green) prices for making a maximum profit are highlighted.

14. Length of longest subsequence

Problem Statement: Given a one-dimensional integer array a of length n, find the length of the longest subsequence that increases before decreasing.

15. Find the longest path in a given matrix

Problem Statement: Given an n*n matrix where all numbers are distinct, find the longest path starting from any cell such that all cells along the path increase in order by 1.

Math and Statistics

16. Find the missing number in the array

Problem Statement: Given an array of positive numbers ranging from 1 to n, such that all numbers from 1 to n are present except one number x, find x.

The input array is not sorted.

17. Find all sum combinations

Problem Statement: Given a positive integer, target, print all possible combinations of positive integers that sum up to the target number.

For example, if we are given input ‘5’, these are the possible sum combinations.

1, 4
2, 3
1, 1, 3
1, 2, 2 
1, 1, 1, 2
1, 1, 1, 1, 1

The output will be in the form of a list of lists or an array of arrays. Each element in the list will be another list containing a possible sum combination.

18. Find the kth permutation

Problem Statement: Given a set of n variables, find their kth permutation. Consider the following set of variables:

Backtracking

19. Regular expression matching

Problem Statement: Given a text and a pattern, determine if the pattern matches the text completely or not at all using regular expression matching. Assume the pattern contains only two operators: . and *. Operator * in the pattern means that the character preceding * may not appear or may appear any number of times in the text. Operator . matches with any character in the text exactly once.

Below is an example of a text and its matching and non-matching patterns.

20. Rat in a Maze

Problem Statement: Consider a rat placed in a square n*n matrix at position (0, 0). Find all possible paths the rat can take to reach its destination (N-1, N-1) from its starting position.

The rat can move vertically and horizontally. Cells with a value of 1 can be traversed, while cells with a value of 0 cannot. The rat cannot visit a cell more than once.

21. Solve the Sudoku

Problem Statement: Given a square matrix grid of 9*9 and configured to represent an incomplete Sudoku puzzle, find a solution that returns a true or false value depending on whether or not the Sudoku can be completed. If a solution is possible, your solution must also return the completed grid.

Graphs

22. Clone a directed graph

Problem Statement: Given the root node of a directed graph, clone this graph by creating its deep copy so that the cloned graph has the same vertices and edges as the original graph.

23. Conduct a Breadth-First Traversal of a given graph

Problem Statement: Starting from the source node, traverse a given graph breadthwise to find the distance between the source node and node n.

24. Check if there’s a path from a source to its destination

Problem Statement: Given a graph n*n with each cell containing a value of 0, 1, 2, or 3, return a true or false value depending on whether or not one can find a path from the source node to the destination node. Each graph will have one source node and one destination node. The graph can be traversed horizontally and vertically.

The cell containing a value of 0 is the source node. A value of 1 represents a wall; this node is impassable. A value of 2 represents a blank cell that can be traversed. A value of 3 represents the destination node.

Sort and Search

25. Find the closest meeting point

Problem Statement: Given n people on a square grid, find the point that requires the least total distance covered by all people to meet at that point.

26. Search for the given key in a two-dimensional matrix

Problem Statement: We are given a two-dimensional array where all elements in any individual row or column are sorted. In such a matrix, we have to search or find the position of a given key.

Be prepared to go over

• Data structures: Arrays, strings, queues, lists, linked lists, stacks, trees, heaps, hash tables, hash maps, hash sets, graphs, and more.
• Algorithms: Breadth-first search, depth-first search, binary search, quicksort, mergesort, dynamic programming, divide-and-conquer, and more.

If you have over 3 years of experience developing software, it is highly likely that you will be asked system design questions, which can be more open-ended.

To get an idea of what to expect from a system design interview, check out the Top 10 system design interview questions for software engineers.

Overview of the Microsoft hiring process

The timeline for the entire process (from submitting your resume to receiving a job offer) takes approximately 1-2 months You are encouraged to use whatever mainstream programming language (e.g., C/C++ or Java) that you are most comfortable with to solve the technical questions.

Interviews

• Prescreening: A recruiter contacts you via email to schedule a 45-minute phone call. They will spend 15 minutes going over your resume and asking behavioral questions. You have the remaining 30 minutes to solve a coding question related to algorithms and data structures in a shared editor.
• Phone interview: The recruiter contacts you within two weeks to schedule a phone interview with a senior developer or engineering manager. Information about potential topics that may be covered during this phone interview will be provided in advance.
• On-site or virtual interview: After passing the phone interview, you will be invited to participate in 4-5 rounds of interviews either in-person at the Microsoft campus or virtually. Each round is an hour long and will be conducted by two members of the team you’re looking to join. These rounds will have both behavioral and technical questions.
• Lunch interview: Halfway through the rounds, you will be taken out to lunch for a more casual conversation. This will take place on the Microsoft campus, or off-campus at a restaurant.
• Final interview of the day: The last round will be conducted by an AS-AP (As-Appropriate) who will have the final say in hiring you.
• HR interview: The hiring manager will go over any remaining behavioral or technical questions not covered in the previous rounds of interviews, make an offer, and discuss compensation.

How to prepare for the interview

Microsoft develops a holistic view of you as a candidate using competency-based questioning in addition to your resume. They want candidates with strong technical skills that align well with the company values.

Wrapping up and next steps

Now that you’re more familiar with the Microsoft interview process, it’s time to make a plan and put it into action! The best candidates come fully prepared, so it’s important to exercise due diligence. We’ve put together an extensive course that will help you quickly identify any gaps in your knowledge, test your skills, and practice using a live, in-browser coding environment.

You can visit our Decode the Coding Interview library. The Decode series exposes you to some of the most frequently asked questions at tech companies and helps solidify your knowledge by contextualizing these problems in real-world applications.

Happy learning!

Related courses

• Grokking Coding Interview Patterns in Java
• Grokking Coding Interview patterns in C++
• Grokking Coding Interview patterns in Python

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