Unlock the Top 20 Coding Questions to Pass LinkedIn Interview

Are you gearing up for a LinkedIn interview and feeling overwhelmed?

You're not alone. Many fresh candidates share common worries about the coding interview process.

At LinkedIn, coding interviews are designed to assess not just your technical skills but also how you approach problems and think on your feet. This can be daunting, especially for those who are new to the job market. But don’t worry, preparing well can make a big difference.

In this blog, we will cover the top 20 coding interview questions that you might encounter at LinkedIn. These questions will help you understand the type of challenges you’ll face and how to tackle them effectively.

Section 1: Understanding LinkedIn’s Interview Process

LinkedIn began in 2002 in the living room of Reid Hoffman.

Officially launched on May 5, 2003, it was designed as a platform for professionals to network and connect with others in their industry.

Initially, LinkedIn grew slowly but steadily. By 2004, it had reached 1 million users. The company continued to add features such as Groups in 2005 and became profitable in 2006.

In 2011, LinkedIn went public, and in 2016, Microsoft acquired the company for $26.2 billion. This acquisition helped LinkedIn expand its services and integrate with Microsoft’s tools.

Today, LinkedIn has over 1 billion members in more than 200 countries and territories. It is widely used for professional networking, job searching, and career development

LinkedIn Interview Process

The LinkedIn interview process typically includes several stages:

• Application and Screening: Submit your resume and complete an initial screening with a recruiter. This often involves a phone call to discuss your background and motivations.

• Technical or Skill Assessment: Depending on the role, you may be asked to complete a technical assessment or skill-based test. For technical roles, this could involve coding tests or problem-solving exercises.

• Phone Interviews: You will likely have one or more phone interviews with hiring managers or team members. These interviews focus on your experience, technical skills, and cultural fit.

• Onsite Interviews: The final stage typically involves onsite interviews or virtual meetings. These sessions can include technical problem-solving, behavioral questions, and discussions about your experience and how you handle various work scenarios.

What LinkedIn Looks For

LinkedIn seeks candidates who are:

• Technically Proficient: For technical roles, a strong understanding of relevant technologies and problem-solving skills are crucial.

• Culturally Fit: They value candidates who align with their company culture and values, such as collaboration, integrity, and customer focus.

• Innovative and Adaptable: LinkedIn appreciates employees who can think creatively and adapt to new challenges.

Types of Questions at LinkedIn Interview

Here are the types of questions you can expect at LinkedIn interview:

1. Behavioral Questions: These questions assess how you've handled situations in the past.

2. Technical Questions: For engineering roles, expect coding problems, system design questions, and technical scenarios. Check out the quick guide to clear system design interview.

3. Situational Questions: These questions explore how you would handle hypothetical situations.

Understand the basics and learn effective tips to clear coding interviews.

Section 2: 20 Coding Problems To Pass LinkedIn Interview

Let us discuss the top 20 coding problems to pass the LinkedIn interview:

1. Find Pivot Index

Problem Statement: Given an integer array nums, determine the pivot index of this array.

The pivot index divides the array in such a way that the sum of the numbers on its left side is exactly equal to the sum of the numbers on its right side.

If the index is at the beginning, the sum to its left is considered zero, similarly for an index at the end.

Return the leftmost pivot index. If no such index exists, return -1.

Example:

• Input: [1, 2, 3, 4, 3, 2, 1]
• Expected Output: 3
• Justification: The sum of the numbers to the left of index 3 (1 + 2 + 3) is 6, and the sum to its right (3 + 2 + 1) is also 6.

Difficulty Level: Easy

Solution: Find Pivot Index

2. Isomorphic Strings

Problem Statement: Given two strings s and t, return true if they are isomorphic. Otherwise, return false.

Two strings s and t are called isomorphic if the characters in string s can be replaced to get string t.

Each character in string t should be replaced with another character while preserving the order of characters as in string s.

Two characters should not map to the same character, but a character may map to itself.

Example:

• Input: s = "abb", t = "cdd"
• Expected Output: true
• Justification: Each character in "abb" can be replaced to match the corresponding character in "cdd" (a->c, b->d) while maintaining a one-to-one mapping.

Difficulty Level: Easy

Solution: Isomorphic Strings

3. **Second Minimum Node In a Binary Tree **

Problem Statement: You are given a non-empty special binary tree consisting of nodes with a positive value, where each node in this tree has exactly two or zero children.

If the node has two children, then the current node's value is the smaller value among its two children.

In other words, the property root.val = min(root.left.val, root.right.val) always holds for each node of the tree.

Given such a binary tree, return the second minimum value in the set made using all the nodes' values in the whole tree.

If no such second minimum value exists, output -1 instead.

Example:

• Input: [4, 4, 5, null, null, 5, 6]

• Expected Output: 5
• Justification: The smallest value is 4, and the second smallest is 5.

Difficulty Level: Easy

Solution: Second Minimum Node In a Binary Tree

4. Minimum Time to Type Word Using Special Typewriter

Problem Statement: You are given a circular keyboard that has all the lowercase English letters ('a' to 'z') laid out in a circle.

You can type a particular character if the point is pointed to that character.

Initially, a cursor points at the letter 'a'.

At each second, you can perform the following operation:

• Move the cursor either one step to the left or right.
• Type the letter where the pointer points currently.

Given a string word, return the minimum number of seconds to type out the characters in a word.

Example:

• Input: “bad”
• Expected Output: 8
• Justification: Start at 'a'. Move to 'b' (1 second), type 'b' (1 second), move to 'a' (1 seconds), type 'a' (1 second), move to 'd' from 'a' (3 second), and type 'd' (1 second). Total = 8 seconds.

Difficulty Level: Easy

Solution: Minimum Time to Type Word Using Special Typewriter

5. Intersection of Two Arrays

Problem Statement: Given two arrays, nums1 and nums2 containing integers, return an array of the intersection of nums1 and nums2.

In the resultant array, each integer should be unique, and elements can be in any order.

Example:

• Input: nums1 = [3,1,2,6,7,8], nums2 = [2,3,4,5,7,9]
• Expected Output: [2,3,7]
• Justification: The numbers 2, 3, and 7 are present in both nums1 and nums2.

Difficulty Level: Easy

Solution: Intersection of Two Arrays

6. Valid Perfect Square

Problem Statement: Given a positive integer num, return true if num is a perfect square or false otherwise.

A perfect square is an integer that is the square of an integer. In other words, it is the product of some integer with itself.

You must not use any built-in library function, such as sqrt.

Example:

• Input: 49
• Expected Output: true
• Justification: (7 * 7) equals 49.

Difficulty Level: Easy

Solution: Valid Perfect Square

7. Sqrt

Problem Statement: Given a non-negative integer x, return the square root of x rounded down to the nearest integer. The returned integer should be non-negative as well.

You must not use any built-in exponent function or operator.

For example, do not use pow(x, 0.5) in C++ or x ** 0.5 in Python.

Example:

• Input: x=8
• Expected Output: 2
• Justification: The square root of 8 is 2.8284, and since we need to return the floor of the square root (integer), hence we returned 2.

Difficulty Level: Easy

Solution: Sqrt

8. Maximum Depth or height of a Binary Tree

Problem Statement: Determine the depth (or height) of a binary tree, which refers to the number of nodes along the longest path from the root node to the farthest leaf node. If the tree is empty, the depth is 0.

Example:

• Input:

• Expected Output: 3
• Justification: The longest path is 1->2->4 or 1->2->5 with 3 nodes.

Difficulty Level: Easy

Solution: Maximum Depth or height of a Binary Tree

9. Rotate List

Problem Statement: Given the head of a linked list and integer k, rotate the list to the right by k places.

Example:

• Input: head = [7, 13, 1], k = 2
• Expected Output: [13, 1, 7]
• Justification: The list [7, 13, 1] when rotated by 2 positions to the right, the last two elements (13 and 1) move to the front, resulting in [13, 1, 7].

Difficulty Level: Easy

Solution: Rotate List

10. Valid Triangle Number

Problem Statement: Given an array of integers nums, return the number of triplets we can make using array elements that can create triangle if we take them as side lengths of a triangle.

A set of three numbers can constitute a triangle if and only if the sum of any two sides is greater than the third side. This condition must hold true for all three combinations of summed sides.

Example:

• Input: nums = [4, 2, 3, 1]
• Expected Output: 1
• Justification: The valid combinations that can form a triangle are (2, 3, 4). The other combinations either do not meet the triangle inequality theorem or are duplicates in a different order.

Difficulty Level: Medium

Solution: Valid Triangle Number

11. Valid Parenthesis String

Problem Statement: Given a string s containing multiple occurrences of characters: '(', ')' and '*', return true if s is valid. Otherwise, return false.

A string is valid if it follows below rules:

• Any left parenthesis '(' must be closed by corresponding right parenthesis ')'.
• Any right parenthesis ')' must have a corresponding left parenthesis '('.
• '*' can be used as a single left parenthesis ')' or a single right parenthesis '(' or an empty string "".

Example:

• Input: s= "*())"
• Expected Output: true
• Justification: The asterisk can be treated as an open parenthesis, making the string "(())."

Difficulty Level: Medium

Solution: Valid Parenthesis String

12. Edit Distance

Problem Statement: Given two strings word1 and word2, return the least number of edits needed to transform word1 to word2. You can perform any one edit from below three in a single operation on Word:

• Insert a character
• Delete a character
• Replace a character

Example:

• Input: word1 = "cat", word2 = "cut"
• Expected Output: 1
• Justification: Only one operation is needed, replacing 'a' with 'u' in "cat" to make it "cut".

Difficulty Level: Medium

Solution: Edit Distance

13. Remove All Ones With Row and Column Flips II

Problem Statement: Given a 0-indexed m x n binary matrix, return the minimum number of operations needed to remove all 1's from the matrix.

In one operation, you can choose any i and j such that:

• 0 <= i < m
• 0 <= j < n
• grid[i][j] == 1 and change the values of all cells in row i and column j to zero.

Example:

• Input: [[1,0,1], [1,1,1], [0,1,0]]
• Expected Output: 2
• Justification: First, choose the cell [0,2], and perform operations. The matrix becomes [[0,0,0],[1,1,0],[0,1,0]]. Then, choose the middle cell [1,1]. The matrix becomes all zeros.

Difficulty Level: Medium

Solution: Remove All Ones With Row and Column Flips II

14. Triplet Sum to Zero

Problem Statement: Given an array of unsorted numbers, find all unique triplets in it that add up to zero.

Example:

• Input: [-3, 0, 1, 2, -1, 1, -2]
• Expected Output: [[-3, 1, 2], [-2, 0, 2], [-2, 1, 1], [-1, 0, 1]]
• Justification: There are four unique triplets whose sum is equal to zero. smallest sum.

Difficulty Level: Medium

Solution: Triplet Sum to Zero

15. Decode Ways

Problem Statement: You have given a string that consists only of digits. This string can be decoded into a set of alphabets where '1' can be represented as 'A', '2' as 'B', ... , '26' as 'Z'.

The task is to determine how many ways the given digit string can be decoded into alphabets.

Example:

• Input: "121"
• Expected Output: 3
• Justification: The string "121" can be decoded as "ABA", "AU", and "LA".

Difficulty Level: Medium

Solution: Decode Ways

16. House Robber II

Problem Statement: You are given an array representing the amount of money each house has. This array models a circle of houses, meaning that the first and last houses are adjacent.

You are tasked with figuring out the maximum amount of money you can rob without alerting the neighbors.

The rule is: if you rob one house, you cannot rob its adjacent houses.

Example:

• Input: [4, 2, 3, 1]
• Expected Output: 7
• Justification: Rob the 1st and 3rd house, which gives 4 + 3 = 7.

Difficulty Level: Medium

Solution: House Robber II

17. Design Add and Search Words Data Structure

Problem Statement: Design a data structure that supports the addition of new words and the ability to check if a string matches any previously added word.

Implement the Solution class:

• Solution() Initializes the object.
• void addWord(word) Inserts word into the data structure, making it available for future searches.
• bool search(word) Checks if there is any word in the data structure that matches word. The method returns true if such a match exists, otherwise returns false.

Note: In the search query word, the character '.' can represent any single letter, effectively serving as a wildcard character.

Example:

• Input: ["Solution", "addWord", "addWord", "search", "search"][[], ["apple"], ["banana"], ["apple"], ["....."]]
• Expected Output: [-1, -1, -1, 1, 1]
• Justification: After adding the words "apple" and "banana", searching for "apple" will return true since "apple" is in the data structure. Searching for "....." will also return true as both "apple" and "banana" match the pattern.

Difficulty Level: Medium

Solution: Design Add and Search Words Data Structure

18. Merge Intervals

Problem Statement: Given a list of intervals, merge all the overlapping intervals to produce a list that has only mutually exclusive intervals.

Example:

• Input: Intervals: [[1,4], [2,5], [7,9]]
• Expected Output: [[1,5], [7,9]]
• Justification: Since the first two intervals [1,4] and [2,5] overlap, we merged them into one [1,5].

Difficulty Level: Medium

Solution: Merge Intervals

19. Same Tree

Problem Statement: Given the roots of two binary trees 'p' and 'q', write a function to check if they are the same or not.

Two binary trees are considered the same if they met following two conditions:

1. Both tree are structurally identical.
2. Each corresponding node on both the trees have the same value.

Example:

• Input: Given the following two binary trees:

• Expected Output: true
• Justification: Both trees are structurally identical and have the same values.

Difficulty Level: Medium

Solution: Same Tree

20. Closest Binary Search Tree Value II

Problem Statement: Given the root of a binary search tree, an integer target, and an integer k, return a 1D array total containing k values from the BST which are closest to the given target value.

You may return the answer in any order.

Example:

• Input: BST = [10,5,15,2,7,null,18], target = 8.5, k = 3

• Expected Output: [7,10,5]
• Justification: The three numbers closest to 8.5 in the BST are 7, 10, and 5.

Difficulty Level: Hard

Solution: Closest Binary Search Tree Value II

Discover everything you need to know about LinkedIn’s Open To Work banner.

Wrapping Up

Preparing for a LinkedIn coding interview can seem challenging, but with the right approach, you can tackle it confidently.

Interviews are not just about testing your knowledge but also about showing how you approach and solve problems. It’s not about giving the right answers but understanding the underlying concepts and being able to explain your thought process clearly.

Therefore, practice these top 20 coding questions to gain a better understanding of what to expect and design solutions effectively.