# Top Java Data Structures Interview Questions and Answers to Practice

Technical interviews at FAANG+ companies fundamentally test your ability to solve complex data structures and algorithms problems. Interview questions about Java Data Structures are frequently asked during coding rounds of technical interviews. The best way to ace tough technical interviews is to sharpen your problem-solving skills by identifying and classifying problems based on inherent patterns.

Preparing thoroughly for Java data structures interview questions by devoting adequate time to honing your problem-solving skills is essential for standing out from the crowd. If you have a technical interview coming up, it is highly recommended that you answer at least 1-2 Java data structures interview questions per day.

In this article, we’ll look at some Java data structures interview questions asked at FAANG+ interviews. These questions will give you an idea of what to expect at these interviews and devise a sound strategy that will help you get through challenging technical rounds.

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Let’s look at some common Java data structures interview questions asked in technical interviews. Here’s what we’ll cover:

- Java Data Structures Interview Questions on Arrays
- Java Data Structures Interview Questions on Linked Lists
- Java Data Structures Interview Questions on Strings
- Java Data Structures Interview Questions on Trees and Graphs
- FAQs on Java Data Structures Interview Questions

Before moving on to Java data structures interview questions, let’s look at some essential data structures and algorithms topics that regularly feature technical interviews at FAANG+ companies.

- Arrays, strings, and linked lists
- Sorting algorithms — quicksort, merge sort, heap sort, etc.
- Hash tables and queues
- Recursion
- Trees and graphs
- Graph algorithms, including greedy algorithms
- Dynamic programming

## Java Data Structures Interview Questions on Arrays

- For a given unsorted array, write a program to find a contiguous subarray that adds to a given number in the array
- For two unsorted arrays where elements are in non-decreasing order, write a code to merge the two arrays such that the new array is sorted
- For a given array of size N-1, containing integers in the range from 1 to N, write a program to find the missing element in the array
- For a given array containing positive integers, write a code to return the sum of the elements of the array
- For a given unsorted array of size N, write a code to rotate it anticlockwise, by D elements
- For a given array of size N, write a code to print the reverse of the array
- For a given array A, write a code to delete the duplicate elements in the array
- For a given array Arr[] containing integer elements, write a code to find the minimum and maximum elements of the array
- For a given array of size N containing distinct integer numbers, write a code to sort the array in the wave fashion
- From a given array containing integer values, write a code to find the maximum subarray of non-negative numbers

*Take a look at the **Concept of Arrays in Java Data Structures** here.*

## Java Data Structures Interview Questions on Strings

- For a given String S, write a code to reverse the string without disturbing the individual words
- For a given String, write a program to print all permutations (of its characters) and return it in a lexicographically sorted fashion
- Write a program function for a given String S to find the longest palindromic substring. A palindromic string reads the same even backward
- For a given String that has its elements represented in Roman Values, write a code to convert the String into integer values
- For a given String S, write a program to remove duplicate elements from the String
- For a given String S, write a code to find the minimum number of elements or characters that need to be inserted to convert it into a palindrome
- For a given String S, write a program to find the length of the longest Substring with distinct values
- For a given String S, write a code to remove successive duplicate characters recursively
- For two strings, A and B, write a program to figure out if B can be obtained by rotating A in at least two places
- Write a program to implement the strstr function

## Java Data Structures Interview Questions on Linked Lists

- How do you insert a node at the end of a Linked List?
- How do you delete a particular node in a Linked List?
- Write a code to reverse a Singly Linked List.
- Write a code to add two numbers represented by Linked Lists
- Write a function to remove the nth node from a Linked List
- Write a program to swap adjacent nodes in a Linked List
- Write a code to reverse a Linked List from position X to position Y
- For a given Linked List, write a code to return the node value where the cycle in question begins
- Write a program to flatten a given multi-level linked list
- Write a code to find the next greater node for a given Linked List
- Write a code to clone a given Linked List with the next random pointer

## Java Data Structures Interview Questions on Trees and Graphs

- For a given binary tree where each node contains a number, find the maximum path sum from one node to the other
- For a given binary tree B, write a function to calculate its height
- For a given binary tree that contains all unique values, write a code to find the lowest common ancestors of the nodes
- For a given binary tree, write a function to connect nodes that are at the same level
- For a given binary tree T, write a function to find its spiral order traversal
- For a given binary tree, write a program that traces its vertical traversal
- For a given binary tree T, write a code to print the bottom view of the tree from left to right
- You're given the root of a binary tree T. Write a program to find out of it is a Binary Search Tree or not
- For a given Directed Graph with V vertices and E edges, write a program that identifies that number of strongly connected components in the graph
- For a given Directed Acyclic Graph, write a program that finds the topological sorting in the graph
- For a given graph with E edges and V vertices, find out whether the graph contains a cycle or not
- For a given directed graph, perform Breadth-First Search
- For a given undirected, connected graph, perform Depth First Search
- Write a code to convert a given binary Tree into a Doubly Linked List
- For two binary trees that are given, write a program to find out if they’re identical or not

*Learn about **AVL in Data Structures and Algorithms** here.*

These Java data structures interview questions will help you thoroughly prepare for your upcoming technical interview. For more problems with optimal solutions, visit our Problems Page.

## FAQs on Java Data Structures Interview Questions

**Q1. What topics should you prepare to solve Java data structures ****interview questions in a technical**** interview?**

To solve Java data structures interview questions, you must be thorough with the following concepts - arrays, strings, linked lists, recursion, hash tables, graphs, trees, and dynamic programming.

**Q2. When can you expect Java data structures interview questions in technical interviews?**

You can expect Java data structures interview questions during the Technical Phone Screen Round and the On-site interview round.

**Q3. Which is the best way to improve your problem-solving skills to solve Java data structures interview questions effectively?**

The best way to improve your problem-solving skills is to identify patterns in the problems you solve and classify problems based on similar patterns. That way, you can apply existing patterns to solve new problems and tackle tricky and challenging problems at the interview.

**Q4. Are Java data structures interview questions asked in systems design interviews?**

No, Java data structures interview questions are asked only in coding interviews of companies and not in systems design interviews.

**Q5. Should you be adept with data structures and algorithms if you give interviews for ML or Security Engineering positions?**

Yes, testing your knowledge in data structures and algorithms is a fundamental interview assessment exercise that FAANG+ companies adopt. Thus, even if you’re applying to ML or Security Engineering positions, you can expect a few DSA problems at your interview.

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