Coding questions vary in difficulty. Some start with simple questions and work their way up to more difficult problems. Others are puzzles and problems that require more complex logic. The key is to be prepared for the challenges that lie ahead. It is better to start from the basics and build up from there. Then, you’ll have the confidence to tackle more complex questions.

## Arrays

Arrays are a core concept in many data structures. They are also a common type of coding interview question. To answer these questions, you must understand how arrays work and how they’re implemented in different programming languages. Typically, an array is composed of several elements and is sorted in some way.

Arrays can be useful in solving many problems, and they can also be a way to test your problem-solving skills. For example, in a common array coding question, you need to determine whether an element in an array has more than one element. If it has more than one element, you must use the ‘equals’ method to determine whether the elements are equal.

## HashMap

A HashMap is a type of array that stores items by key and value. If you are applying for a technical job, you may be asked about this data structure during your interview. This will allow you to show how well you understand the fundamentals of computer architecture. In addition, the question might be intended to test whether you can explain the impact of certain actions. Therefore, it is a good idea to study possible HashMap interview questions and prepare effective responses.

The first thing you should know about HashMaps is that they can store duplicate values. You can do this by using the keySet() method. This method returns a collection, not an ordered list. HashMaps are safe to use when you have multiple threads running concurrently.

## HashTable

A hash table is a data structure used to store a list of keys and values. It is simple to use and efficient. Employers expect candidates to know the basics of this data structure, so understanding how to code with HashTables will increase your chances of getting hired. The following are some questions you might be asked when interviewing for a job.

o What’s the difference between HashMap and HashTable? HashMap is the more commonly used of the two, while Hashtable is less common. The difference between the two is that the former does not allow null values.

## Array comparison

One of the most commonly asked questions in coding interviews is the Array comparison question, or Q39 for short. This is a question in which the programmer must find the first non-repeating number from an array of integers. Then, they must subtract the first number from the sum of all other elements. If the two sums are different, the missing number is found.

The solution to this question is to use a hash map. This will iterate over the array elements until the resulting number is equal to the sum of the two arrays. This will be a good exercise for learning about space and time-complexity optimization.

## String comparison

If you’re in the process of learning Java, you should start with learning about the concept of String comparison. This part of the language is used to compare and order strings in an array. It is important not to confuse the comparison operator “=” with the assignment operator “=”. Learning the basics of String comparison will help you prepare for an interview and open the door to learning more about the language. The more familiar you are with the language, the better your chances will be of landing a job.

String comparison **coding questions** are a common part of coding interviews and software engineering interviews. A program that compares two strings has to handle edge cases and different types of input. For instance, a string may contain parentheses, so the program should determine whether the parentheses match.

## Hash table

Hash table is a data structure which stores keys and values. It is a very efficient and easy-to-use type of data structure. Many employers expect candidates to be familiar with hash tables, so learning how to use them properly will increase your job prospects. Listed below are the main uses of a hash table.

The hash table is useful for storing many small items with a common key. It can be retrieved quickly with a simple search on the key. This data structure is useful for mapping values to different types. You can search for a value in a hash table in O(1) time if you know the value of the key.

## Hash table comparison

If you’re thinking about the Hash table comparison in coding questions, consider the idea of a series of buckets. For example, in an alpha-numeric hash-code implementation, there would be a bucket for each letter of the alphabet. All items with a hash code that starts with a certain letter would be put into that bucket. This way, if you have 200 objects, you would only need to look up the first 15 of those objects, rather than the entire set.

A hash function is a mathematical function that maps a set of elements to an array of values. It is based on the concept of parity-preserving bit operations such as divide and multiply. Using this type of hash table is the natural way to check cyclic lists.