The dream of every programmer is to become not just a good, but also a great programmer. We all want to achieve our goals and to achieve our goals, we must have a great plan with us. In this context, we have decided to provide a complete guide for Arrays interview preparation, which will help you to tackle the problems that are mostly asked in the interview, such as What is an Array, What is Array in C language, How do you initialize an Array in C, How to sort an Array, etc. We have also covered the topics such as Top Theoretical interview questions and Top interview coding questions in this complete guide for Array interview preparation.
What is an Array?
An array is a collection of items of the same variable type stored that are stored at contiguous memory locations. It’s one of the most popular and simple data structures and is often used to implement other data structures. Each item in an array is indexed starting with 0.
We can directly access an array element by using its index value.
Basic terminologies of array
 Array Index: In an array, elements are identified by their indexes. Array index starts from 0.
 Array element: Elements are items stored in an array and can be accessed by their index.
 Array Length: The length of an array is determined by the number of elements it can contain.
Representation of Array
The representation of an array can be defined by its declaration. A declaration means allocating memory for an array of a given size. Arrays can be declared in various ways in different languages. For better illustration, below are some languagespecific array declarations.
C++

C

Java

C#
However, the above declaration is static or compiletime memory allocation, which means that the array element’s memory is allocated when a program is compiled. Here only a fixed size (i,e. the size that is mentioned in square brackets []) of memory will be allocated for storage, but don’t you think it will not be the same situation as we know the size of the array every time, there might be a case where we don’t know the size of the array. If we declare a larger size and store a lesser number of elements will result in a wastage of memory or either be a case where we declare a lesser size then we won’t get enough memory to store the rest of the elements. In such cases, static memory allocation is not preferred.
Is it possible to create dynamic array?
The answer is Yes. It is possible to allocate memory dynamically. So, dynamic memory allocation is the process of assigning the memory space during the execution time or the run time.
Below are the languages that support dynamic memory allocation:
C++
Java

Python3

C#

Javascript

PHP

Why Array Data Structures is needed?
Assume there is a class of five students and if we have to keep records of their marks in examination then, we can do this by declaring five variables individual and keeping track of records but what if the number of students becomes very large, it would be challenging to manipulate and maintain the data.
What it means is that, we can use normal variables (v1, v2, v3, ..) when we have a small number of objects. But if we want to store a large number of instances, it becomes difficult to manage them with normal variables. The idea of an array is to represent many instances in one variable..
Types of arrays:
There are majorly two types of arrays:
 Twodimensional array: 2D Multidimensional arrays can be considered as an array of arrays or as a matrix consisting of rows and columns.
 Threedimensional array: A 3D Multidimensional array contains three dimensions, so it can be considered an array of twodimensional arrays.
Types of Array operations:
 Traversal: Traverse through the elements of an array.
 Insertion: Inserting a new element in an array.
 Deletion: Deleting element from the array.
 Searching: Search for an element in the array.
 Sorting: Maintaining the order of elements in the array.
 Arrays allow random access to elements. This makes accessing elements by position faster.
 Arrays have better cache locality which makes a pretty big difference in performance.
 Arrays represent multiple data items of the same type using a single name.
 Arrays store multiple data of similar types with the same name.
 Array data structures are used to implement the other data structures like linked lists, stacks, queues, trees, graphs, etc.
 As arrays have a fixed size, once the memory is allocated to them, it cannot be increased or decreased, making it impossible to store extra data if required. An array of fixed size is referred to as a static array.
 Allocating less memory than required to an array leads to loss of data.
An array is homogenous in nature so, a single array cannot store values of different data types.  Arrays store data in contiguous memory locations, which makes deletion and insertion very difficult to implement. This problem is overcome by implementing linked lists, which allow elements to be accessed randomly.
 They are used in the implementation of other data structures such as array lists, heaps, hash tables, vectors, and matrices.
 Database records are usually implemented as arrays.
 It is used in lookup tables by computer.
 It is used for different sorting algorithms such as bubble sort insertion sort, merge sort, and quick sort.
Top theoretical interview questions
S.no  Question  Answer 

1  What will happen if you do not initialize an Array?  View 
2  Why is the complexity of fetching a value from an array be O(1)  View 
3  When should you use an Array over a List?  View 
4  What is a circularly sorted array?  View 
5  Comparing two arrays using hashmap?  View 
6  “What are the advantages of a linked list over an array? In which scenarios do we use LinkedList and when Array?”  View 
7  How do I iterate rows and columns of a multidimensional array?  View 
8  What is meant by Sparse Array?  View 
9  What are the benefits of Heap over Sorted Arrays?  View 
10  Is there any difference between int[] a and int a[]?  View 
11  Can we declare array size as a negative number?  View 
12  We know that Arrays are objects so why cannot we write strArray.length()?  View 
13  What are the advantages of Sorted Arrays?  View 
14  What defines the dimensionality of an Array?  View 
15  How to check array contains a value or not?  View 
16  How to create an array/list inside another array/list?  View 
17  How to get the largest and smallest number in an array?  View 
18  How can I return coordinates/indexes of a string in a multidimensional array?  View 
19  How do I remove objects from an array in Java?  View 
20  How does C allocate data items in a multidimensional array?  View 
21  Get adjacent elements in a twodimensional array?  View 
22  C++ How to use and pass a 3dimensional char array?  View 
23  Anonymous Array in Java  View 
24  What is the default value of Array in Java?  View 
25  How to copy an array into another array?  View 
26  How to iterate an array in java?  View 
27  How to merge two sorted Arrays into a Sorted Array?  View 
28  Can we make the array volatile in Java?  View 
29  What is the logic to reverse the array?  View 
30  How to get the index of an array element?  View 
31  Can we extend an array after initialization?  View 
32  How to fill elements (initialize at once) in an array?  View 
33  Difference between Array and String in Java  View 
34  Print all subarrays with 0 sum  View 
35  Equilibrium index of an array  View 
36  How to check array contains a value or not?  View 
37  How to get the top two numbers from an array?  View 
38  How to implement 3 Stacks with one Array?  View 
Top 50 interview coding question
Easy Problems on Arrays
S.no  Question  Article  Practice 

1  Peak Element  View  Solve 
2  Find the minimum and maximum element in an array  View  Solve 
3  Write a program to reverse the array  View  Solve 
4  Write a program to sort the given array  View  Solve 
5  Find the Kth largest and Kth smallest number in an array  View  Solve 
6  Find the occurrence of an integer in the array  View  Solve 
7  Sort the array of 0s, 1s, and 2s  View  Solve 
8  Subarray with given Sum  View  Solve 
9  Move all the negative elements to one side of the array  View  Solve 
10  Find the Union and Intersection of the two sorted arrays  View  Solve 
Medium Problems on Arrays
S.no  Question  Article  Practice 

1  Write a program to cyclically rotate an array by one  View  Solve 
2  Find the missing integer  View  Solve 
3  Count Pairs with given sum  View  Solve 
4  Find duplicates in an array  View  Solve 
5  Sort an Array using the Quicksort algorithm  View  Solve 
6  Find common elements in three sorted arrays  View  Solve 
7  Find the first repeating element in an array of integers  View  Solve 
8  Find the first nonrepeating element in a given array of integers  View  Solve 
9  Subarrays with equal 1s and 0s  View  Solve 
10  Rearrange the array in alternating positive and negative items  View  Solve 
11  Find if there is any subarray with a sum equal to zero  View  Solve 
12  Find the Largest sum contiguous Subarray  View  Solve 
13  Find the factorial of a large number  View  Solve 
14  Find Maximum Product Subarray  View  Solve 
15  Find the longest consecutive subsequence  View  Solve 
16  Find the minimum element in a rotated and sorted array  View  Solve 
17  Max sum in the configuration  View  Solve 
18  Minimum Platforms  View  Solve 
19  Minimize the maximum difference between the heights  View  Solve 
20  Minimum number of jumps to reach the end  View  Solve 
21  Stock Span problem  View  Solve 
23  Find a triplet that sums to a given value  View  Solve 
23  Smallest positive missing number  View  Solve 
24  Find the row with a maximum number of 1’s  View  Solve 
25  Print the matrix in a Spiral manner  View  Solve 
26  Find whether an array is a subset of another array  View  Solve 
27  Implement two Stacks in an array  View  Solve 
28  Majority Element  View  Solve 
29  Wave Array  View  Solve 
30  Trapping Rainwater  View  Solve 