Top Array Coding Problems for Interviews

Have you just graduated from your college recently, looking for a job or are you trying to switch to another job?

Whatever the reason is, you need to always prepare for your interview in a smart way. Moreover, if you are preparing for a coding interview, an array is one of the important topics that you can never miss!

An array is a quite more extensive topic than you have anticipated and this is why going through each and every topic is not easy.

Therefore, we have listed some common array coding questions that you must prepare before appearing for your interview.

So, let’s begin with all the questions and solutions for the array coding questions!

List of All Important Questions

1.    How to merge two sorted arrays?

In this problem, you will be given two sorted arrays and you will have to merge all their elements and contents. To merge two sorted arrays, you can follow two methods including the naive or brute force method or you can use dynamic programming. Generally, dynamic programming is preferred over any other method because of its time and space complexity.

For example, there are two arrays, A1={ 1, 2, 3, 4} and A2= { 5, 6, 7}.

The output should be A3= {1, 2, 3, 4, 5, 6, 7}.

2.   How to count the frequency of an element in the array?

This question is generally also asked as a dynamic programming interview questions. In this question, you need to analyse the frequency of the elements appearing in the array. For this, you will have to create a function or you can use hashing for the same.

For example, the given array is A1= {1, 3, 5, 2, 1}

The output will be like this:

1: 2

3: 1

5: 1

2: 1

3.   How to move all the zeros at the end of an array?

This is one of the medium-level array coding questions that you will encounter which may use a bit more logic. In this problem, you will have to write code to move all the zeros at either the beginning or the end of the array. For this, you can use two markers and run them to swap locations.

For example, if the given input array is A= { 1, 0, 5, 0, 0, 3}

The output of the program will be A={ 0, 0, 0, 1, 5, 3}.

4.   How to rotate an array?

Rotating an array means that you will have to shift the location of all elements in the array by d positions. For this, either you can use a temporary array or you can rotate the elements one by one.

For example, if the given array is A={1, 2, 3, 4} and d= 2

The output of the program will be A= { 3, 4, 1, 2}.

5.   How to find the median of two sorted arrays?

In this problem, you will be given two arrays of sorted order. You will have to find the median of these arrays considering that there are N elements in the first array and N elements in the second array. To do that, you can also follow a simple mathematical approach in your code.

For example, you are given two arrays, A1={ -5, 3, 6, 12, 15} and A2= {-12, -10, -6, -3, 4, 10}

The median of these arrays will be 3.

6.   How to find the longest increasing subsequence?

In this problem, you will have to find the subsequence in which all the elements are present in sorted and increasing order. For this, you can either use recursion or dynamic programming depending on the requirements.

For example, the given array is A= { 1, 2, 4, 3, 2, 6}

The length of the longest increasing subsequence of this array will be 4.

7.   How to resolve the shortest unsorted continuous subarray?

Here, you will be given an unsorted array and you will have to find the subarray of minimum length in such a way that sorting all these arrays will create a complete sorted array. To resolve the problem, you will first have to find the required subarray and then check if sorting the found array sort the complete array or not.

8.   What do you mean by the maximum product subarray problem?

In the maximum product subarray problem, you will be provided with an integer array and you will have to find the subarrays containing the product of all its elements. The output of the program must return the maximum product of the numbers possible with all the subarrays. Generally, two approaches can be used to do this.

Either you can consider all subarrays and then find the solution or you can simply use two variable to manage the current minimum and maximum product.

For example, if the given array is A= { 6, 4, 5, 10, 8, 0}

The maximum product will be 1600.

9.   How to search for insert position?

You will be given a sorted array and integer N. Here, you will have to check if K is present in the array or not. In case it is not present, you need to find an index where you can enter k and keep the array sorted. You can use binary search to resolve the problem.

For example, if the given array is A= { 1, 3, 4, 5, 6} and K= {3 }

The output will be 1.

10.   How to convert a sorted array to the binary tree?

In this problem, you will have to create a binary tree from the sorted array. For this, you can create a binary tree by finding elements of the array.

Conclusion

An Array is one of the fundamental topics that a programmer must be well-versed in to crack the toughest coding interview. However, going through all the concepts from the beginning to advanced every time is not feasible for anyone.

Therefore, we have listed all important array coding questions to save all your efforts of going through every concept individually and revising each of them.

We have also provided you with the solutions to ensure that you do not have to go any further to find solutions. So, keep practising and crack your next interview with ease.