Top 20 Beginner Programming Interview Questions and Answers

Programming interview questions are an integral part of any interview related to development. The specific programming language may not be the question, but deep knowledge of the core programming concept is always required.

From the perspective of a programming interview, success or failure usually depends on your coding skills. Here is a discussion of the top 20 essential questions about programming interview questions, which will help you crack your interview and get into your dream job.

So, without wasting time, let’s break into these Programming Interview Questions! There are two categories in this, Coding questions for conceptual understanding and programming questions.

Coding questions for Conceptual Understanding

This section covers a few coding interview questions that check the conceptual understanding of the candidate.

1. What is a Data Structure?

A data structure is an organized method for storing, organizing, and managing data so it can be accessed and altered proficiently. It defines how data should be stored in memory and describes how that data will be manipulated in order to implement diverse operations.

Different data structures are used daily, such as arrays, trees, graphs, and linked lists. There are the data structures employed in solving Programming Interview Questions and mastering them, which plays a fundamental role in many algorithms and problem-solving techniques.

In many programming interview questions, understanding when and how to use the appropriate data structure can greatly enhance the efficiency and performance of your solution.

2. What is Array?

An array is a data structure that stores a collection of items at contiguous memory locations. All the items stored in an array are of the same data type, which enables efficient organization of related values and permits operations like sorting and searching to be easily implemented.

The array is a fundamental concept and many Programming Interview Questions are given in terms of arrays because an array provides basic elements for many algorithms and problem-solving techniques Source: geeksforgeeks

Source: GeeksforGeels

3. What is a Linked List and mention its types?

The linked list is considered a linear data structure, but unlike the array, the elements of the linked list are stored in consecutive memory locations. It consists of a sequence of nodes, each of which contains a data value and a reference or pointer to the next node in the sequence.

Each node therefore leads to another node, thus forming a chain-like structure. It is one of the most common data structures featured in any programming interview question because its nature is dynamic, and because it uses memory efficiently.

There are three main types of linked lists:

• Singly Linked List: Each node points to the next node.
• Doubly Linked List: Every node contains a reference to the next node and one to the previous node.
• Circular Linked List: The last node points back to the first node, hence the name circular chain.

Source: Medium

4. What is a Stack and its types?

A stack is a linear data structure that follows the principle of LIFO, or Last In First Out. The last element added would be the first one to be removed. Elements in a stack can only be accessed starting from the topmost down to the bottom element.

Stacks are met very often in Programming Interview Questions because they are straightforward, and used in many algorithms. There are two main types of stacks that are frequently discussed in Programming Interview Questions:

• Static Stack: One that is implemented with an object fixed size, by using arrays.
• Dynamic Stack: A stack can’t have a fixed size; it allows flexible memory allocation since stacks are usually implemented as linked lists.

5. What are the concepts proposed in OOPs?

Object-Oriented Programming (OOPs) proposes the following concepts of greater importance:

• An object: A real-world entity with some state and specific behavior, which is considered to be an instance of a class.Class: A logical entity that constitutes the blueprint for creating or instantiating objects.
• Inheritance: The ability of an object, including its properties and behaviors, to inherit all from another parent object provides the foundation of reusability of code.
• Polymorphism: An operation can be carried out in different ways. This is done in Java by method overloading and method overriding.
• Abstraction: Hides the internal working of an application, exposes its functionality only. Abstract classes and interfaces are used in Java for abstraction.
• Encapsulation: Wrap data and code together into one unit to have better control and security.

Understanding these OOP’s principles is the way to cracking Programming Interview Questions, as these principles are the root of most problem-solving techniques. This is a topic frequently asked in Programming Interview Questions and may lead to further discussion depending on the candidate’s response.

6. What is a Binary Search Tree?

A binary search tree, or BST, is a data structure that facilitates the storage of data in a way so that its retrieval becomes highly efficient. A key property of a BST is:

• Left: In left subtree, all the nodes have values smaller than the value of the parent node.
• Right: The nodes in the right subtree are greater than or equal to the parent node value.

This way, data can be searched, inserted, and deleted quicker. Binary Search Trees are heavily used in many Programming Interview Questions because they are the foundation to most optimization techniques of operations. One must understand BSTs to solve the majority of programming interview questions related to managing data and optimizing search operations.

7. What is the difference between Linear and Non-linear Data Structures?

Analyzing whether data structures are linear or non-linear is important while solving Programming Interview Questions because a different choice affects the entire amount of performance and efficiency. Such data structures are often utilized in most of the Programming Interview Questions specifically when the goal of improving algorithms is in place and when one needs to solve the complex problem.

8. What are the types of sorting algorithms?

Sorting algorithms are utilized to sort data in a given way, either in ascending or descending order. To solve your programming interview questions, it is very important to know different sorting algorithms that help you better optimize performance and data management. Below are the kinds of sorting algorithms:

• Selection Sort: Selection sort repeatedly finds the smallest (or largest) element from the unsorted part and swaps it with the first unsorted element. It’s easy to comprehend but inefficient for long lists.
• Insertion Sort: The insertion sort algorithm constructs the sorted list one element at a time by repeatedly inserting the current element into its proper position. It is useful for small datasets or lists that already partially sorted.
• Merge Sort: The merge sort algorithm is divide-and-conquer. It divides the array into its halves, then it sorts each half and merges them back. Merge Sort is quite efficient and stable.
• Quick Sort: The other divide-and-conquer algorithm Quick Sort chooses a pivot element and partitions the array around the pivot then sorts the partitions recursively. It is one of the fastest sorting algorithms, but performance issues may sometimes arise.
• Heap Sort: This sort algorithm transforms the array into a binary heap structure and repeatedly extracts the largest element and puts it at the last of the array. It is effective but quite less preferred when compared to Quick Sort and Merge Sort.
• Radix Sort: Radix Sort works on digit or bit levels to sort data. It is used for integers.

Source: Medium

It’s a non-comparing sort algorithm and could be quicker for some kinds of data. These sorting algorithms are of great importance in solving many of the Programming Interview Questions, mainly when optimization or the ratio of performance has to be the primary factor.

9. How does variable declaration affect memory?

The memory allocated for a variable depends on its type. When you declare a variable, the system reserves a certain amount of memory based on the type of data that your variable is going to hold. For example, if the variable is declared as an “integer type,” it will reserve 32 bits of memory for that variable. In fact, this is the key to almost all the solutions in Programming Interview Questions. The memory required for declaring any variable is very important and needs to be detected to optimize code performance.

10. What are Dynamic Data Structures?

Dynamic data structures are designed to change their size during the program’s runtime, expanding or shrinking as needed. This type of flexibility allows it to be used in an extremely flexible manner for handling and managing data because it can adapt the size according to the data that is to be processed.

Important Features:

• Flexible Size: Dynamic data structures do not have a fixed size. When elements are added, their size may increase; if an element is removed, then their size may decrease.
• Efficient Data Handling: This flexibility ensures efficient data handling because the structure will accommodate changes in the amount of data.

Examples

• Linked Lists: Supports for dynamic insertion and deletion of elements.
• Stacks and Queues: In some operations, they grow or shrink.

Dynamic data structure is one term that often comes across in Programming Interview Questions as an assessment of whether a candidate has understood the key ideas and indeed knows how to handle data correctly. Concepts serve as foundational approaches towards solving significant problems while trying to demonstrate an excellent ability to handle data, very often tested in Programming Interview Questions.

Programming Questions

This set of coding interview questions tests the programming expertise of candidates and delves deep into various related aspects.

11. How to reverse a string in Java in Programming Interview Questions

• Declare a String: First define the string you want to reverse.
• Get the String Length: Determine the size of a string and how many times you will have to iterate over it.
• Loop Through Characters: Iterate from the first character to the last in the string.
• Build the Reversed String: Append each character to a new string in reverse order.

Here’s an example on how to reverse a string in Java:

String str = "hello";

String reverse = "";

int length = str.length();

for (int i = 0; i < length; i++) {

         reverse = str.charAt(i) + reverse;

}

System.out.println(reverse);

12. How do you determine if a string is a palindrome?

A string is said to be a palindrome if it reads the same backward as it was forward. In order to verify whether the string is a palindrome or not, you just have to reverse the original string and compare it with the reversed copy of the original string. Then if both are the same, the string is a palindrome.

Here is a simple Java program that checks whether a given string is a palindrome, which happens to be a very common question during programming interviews:

String str = "madam";

String reverse = "";

int length = str.length();

for (int i = length - 1; i >= 0; i--) {

         reverse += str.charAt(i);

}

if (str.equals(reverse)) {

          System.out.println(str + " is a palindrome.");

} else {

            System.out.println(str + " is not a palindrome.");

}

Also read: Top Senior Software Engineer Interview Questions Asked in Tech Interviews

13. How to Find the Number of Occurrences of a Character in a String?

You just iterate through the string and compare each character. Every time you find a match, you increment the count. That is typically a topic in Programming Interview Questions to assess basic, fundamental string handling skills.

How do you do that?

• You initialize a counter to zero.
• Iterate over all the characters in the given string.
• For each time the character matches the target character, increase the counter.

Program: 

int count = 0;

char search = 'a';

for (int i = 0; i < length; i++) {

       if (str.charAt(i) == search) {

             count++;

        }

}

System.out.println(count);

14. How would you count the vowels and consonants in a String?

To count the number of vowels and consonants in a string, do this:

• Initialize counters: set up variables for counting vowels and consonants.
• Loop Through the String: Loop through each character in the string.
• Check and Count: If the character is a vowel, then add one to the vowel counter. Otherwise, increment the consonant counter.
• Print-Out Output: Print out the counts of both vowels and consonants.

This method is often used on the Programming Interview Questions to determine if you have the ability to process basic string processing as well as conditional logic.

Program: 

public class VowelConsonantCount {

      public static void main(String[] args) {

          // Initialize the string

          String str = "Hello World";

            // Initialize counters for vowels and consonants

            int vowelCount = 0;

             int consonantCount = 0;

             // Convert the string to lowercase to make comparison case-insensitive

             str = str.toLowerCase();

             // Loop through each character in the string

              for (int i = 0; i < str.length(); i++) {

                   char ch = str.charAt(i);

                // Check if the character is a vowel

                  if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {

                      vowelCount++;

}

// Check if the character is a consonant

else if (ch >= 'a' && ch <= 'z') {

       consonantCount++;

     }

}

          // Print the results

           System.out.println("Number of vowels: " + vowelCount);

           System.out.println("Number of consonants: " + consonantCount);

               }

}

15. How to get the matching elements in an integer array?

To find and print the matching elements within an array, you can perform the following steps –

• Declare an Array: Declare the array with the elements that you want to check.
• Use Nested Loops: Create two loops to compare each element with every other element in the array.
• Print Matches: If match elements are found during comparison then print them.

This is a very commonly used approach while asking you Programming Interview Questions to check your ability to handle arrays and nested loops.

Program:

i

int[] a = { 1, 2, 3, 4, 5, 1, 2, 6, 7 };

  for (int m = 0; m < a.length; m++) {

         for (int n = m + 1; n < a.length; n++) {

              if (a[m] == a[n])

System.out.print(a[m]);

   }

}

Also Read: Top 30 Test Engineer Interview Questions

16. Implement the bubble sort algorithm?

To implement the bubble sort algorithm, you can follow the below steps:

• Explanation: Initialize Array: “int[] a” which will accept the elements to be sorted.
• Outer Loop: Iterate ‘k from 0’ to ‘a.length – 1’, so that the complete array is sorted.
• Inner Loop: Iterate ‘l from 0’ to ‘a.length – k – 1’ for comparison of adjacent elements to swap if necessary.
• Swap Elements: ‘if a[l]>a[l + 1]’, swap.
• Print Sorted Array: print array elements in ascending order.

This is a rather good example that shows the Bubble Sort algorithm very clearly, and is quite apt for Programming Interview Questions where simple algorithms for sorting data are emphasized.

Program:

Program: int[] a = { 1, 2, 7, 6, 4, 9, 12 };

// Perform Bubble Sort

for (int k = 0; k < a.length - 1; k++) {

           for (int l = 0; l < a.length - k - 1; l++) {

                  // Compare adjacent elements

                   if (a[l] > a[l + 1]) {

                       // Swap if the element is greater than the next element

                        int t = a[l];

                         a[l] = a[l + 1];

                          a[l + 1] = t;

           }

     }

}

 // Print sorted array

for (int i : a) {

               System.out.print(i + " ");

}

17. How would you implement the insertion sort algorithm?

In this sorting technique, we assume that the very first element of our array is already sorted. Then we take the second one and store it apart in some separate variable called the “key.” Then we compare that key element with the elements on its left to the right, then we put the key element to its position to sort the first two elements.

We repeat this process with each of the following elements. We compare and insert it in its appropriate location relative to what is already sorted in the array. And, eventually, by repetitions of these processes, it sorts all elements in an array.

Program: 

int[] a = { 12, 11, 13, 5, 6 };

for (int i = 1; i < a.length; i++) {

     int key = a[i];

      int j = i - 1;

             // Move elements of a[0..i-1] that are greater than key

              while (j >= 0 && a[j] > key) {

                    a[j + 1] = a[j];

                      j--;

       }

        a[j + 1] = key;

}

// Print sorted array

for (int num : a) {

           System.out.print(num + " ");

}

18. Write a program to reverse an array?

You should traverse only the first half of the array to reverse an array, and in every pass you swap the element at the current index from the start with the one at the corresponding index from the end. This ensures that all the elements are swapped correctly.

Program: 

int[] a = { 1, 2, 7, 6, 4, 9, 12 };

for (int i = 0; i < a.length / 2; i++) {

     int temp = a[i];

      a[i] = a[a.length - i - 1];

      a[a.length - i - 1] = temp;

}

// Print reversed array

for (int num : a) {

        System.out.print(num + " ");

}

Also read: Internet of Things (IoT) MCQs with Answers

19. How would you exchange two values without the use of a third variable?

• Declare and Initialize: Declare two variables ‘a’ and ‘b’ with allocated initial values.
• Sum: Add ‘a’ and ‘b’ together in ‘b’.
• Swap Values: Subtract the new value of ‘b’ with the summation from ‘a’, in order to update ‘a’ with the old value of ‘b’.

Next, one subtracts the new value of ‘a’ from the sum ‘b’, keeping only in memory the old value of ‘a’This makes it possible to interchange the values of ‘a’ and ‘b’ without using a temporary variable.

Program: 

public class SwapVariables {

     public static void main(String[] args) {

               // Declare and initialize variables

                int a = 5;

                int b = 10;

                 // Print original values

                 System.out.println("Before swapping:");

                  System.out.println("a = " + a)

System.out.println("b = " + b);

   // Calculate sum and perform the swap

    b = a + b;  // b now holds the sum of a and b

    a = b - a;  // a is now the original value of b

     b = b - a;  // b is now the original value of a

     // Print swapped values

      System.out.println("After swapping:");

      System.out.println("a = " + a);

       System.out.println("b = " + b);

    }

}

20. Print a Fibonacci series using recursion?

The Fibonacci numbers are the following integer sequence:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …….

We can compute these using the mathematical formula used in the Fibonacci recursive function.

public static int fibonacci(int n) {

if (n <= 1)

           return n;

     return fibonacci(n - 1) + fibonacci(n - 2);

}

public static void main(String args[]) {

   int n = 10;

   System.out.println(fibonacci(n));

}

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FAQs: Programming Interview Questions

Q1. What are the most common programming interview questions?

Typical questions are about data structures, algorithms, string manipulation issues, and problem solving.

Q2. How to prepare for a programing interview?

Practice code problems on sites like LeetCode, learn algorithms and do practice mock interviews in timed conditions.

Q3. How to tackle complex problems when faced in a programming interview?

Take the problem into parts, explain thought process and get all the testings done.

Q4. What if I face a tough coding problem at an interview?

Communicate your thought process, ask clarifying questions and discussion of possible solutions, even if you can’t solve it completely.

Q5. How important is debugging in programming interviews?

Debugging is very important, because it helps determine where the error lies in your code and how strongly you can make a solution.

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