java recursion interview questions

The 6 Core Recursive Patterns for Interviewing

In this article, we will discuss the top programming interview questions involving Recursion in Java.

However, if you are looking for conceptual interview questions in Java, please refer following articles :50+ Frequently asked Java Interview QuestionsJava 8 Interview Questions

It takes a sizeable amount of time to prepare for a coding interview. There are so many different topics, data structures, and algorithms to go over. Recursion is one of the most important algorithm types. Because it is the basis for so many important algorithms like divide and conquers, graph algorithms, dynamic programming, some tree-based searching and sorting algorithms, and many more. It is unavoidable. So it is important to have some practice before going to a coding interview.

It will take a lot of practice to become good at recursion. But this is a good idea to have a look at these problems before going to an interview. Nobody can guarantee the interview questions but preparing different patterns of coding questions is the key. But whatever interviews I faced till now, they never gave me any very hard problems. They typically ask questions to test the knowledge and the overall approach towards a problem.

This article will focus on the basic questions on recursion that are very common and popular in basic coding interviews. If you search in Google, you will find most of these questions here and there out there anyway. I am just compiling some of the common patterns of interview questions here for you. You will see a few different patterns of recursive algorithms here.

12. Implement Two Stacks using one Array

Problem Statement:

“Create class TwoStacks that uses a single array to generate two stacks. Your class will have the following methods:”

  • Input: an integer
  • Output: inserts the given value in the first stack i.e. stack1
  • Input: an integer
  • Output: inserts the given value in the second stack i.e stack2
  • Output: returns and remove the top value of stack1
  • Output: returns and remove the top value of stack2
  • You’re supplied the following code to begin your solution:

    Solution and Explanation: main.javaTwoStacks.java

    Time Complexity: O(1)O(1)O(1)

    This implementation is space-efficient as it utilizes all of the available space. It doesn’t cause an overflow if there is any space available in the array.

    The tops of the two stacks are the two extreme ends of the array. The first stack starts from the first element at index 0, and the second starts from the last element.

    The first element in stack2 is pushed at index (maxSize-1). Both stacks grow (or shrink) in the opposite direction.

    To check for overflow, all we need do is check for space between the top elements of both stacks, as reflected in the code.

    Stop grinding through endless practice questions, and start breaking down 100+ real-world problems. Practice as you learn with hands-on coding environments inside your browser. No need to switch to your IDE, download an SDK, or scrub through videos.

    FAQ

    Are recursion questions asked in interview?

    Interviewers love to ask recursion interview questions because they truly push interviewees to the limit, and allow interviewers to differentiate between those candidates who are just good and those who are exceptional. Not only that, but recursive techniques tend to bleed into almost every other category of question.

    How important is recursion in interview?

    Recursion is one of the most important algorithm types. Because it is the basis for so many important algorithms like divide and conquers, graph algorithms, dynamic programming, some tree-based searching and sorting algorithms, and many more. It is unavoidable.

    What is recursion in Java with example?

    In Java, a method that calls itself is known as a recursive method. And, this process is known as recursion. A physical world example would be to place two parallel mirrors facing each other. Any object in between them would be reflected recursively.

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