How to check if a given Tree is a Binary Search Tree in Java? Example Tutorial

Hello guys, if you are preparing for a coding interview then you may know those binary tree problems are not easy to solve on coding interviews and I have seen many candidates struggling to do post-order traversal and checking if a given binary tree is a binary search tree or not. If you want to succeed in the coding interview, you need to prepare well on binary trees in general. One way to prepare better is solving common binary tree coding problems like this one, where you need to find if the given tree is BST or not. There are a lot of things that would tell us if a tree is a binary search tree. But before we get to that, we need to understand what a binary tree is.

Radix sort in Java with Example

Hello guys, in one of the interview I was asked to name any O(n) sorting algorithm. I was shocked because I only knew about QuickSort and Mergesort whose best time is O(NLogN), so I couldn't answer that question. After the interview, the first thing I did was to Google about O(n) sorting algorithm and I was surprised to find that there are many algorithms like Radix Sort and Counting Sort and Bucket Sort which can provide O(n) performance. So, I learn them and wrote articles about them like in previous article I explained about Counting Sort algorithm and in this article, I will explain Radis sort like what it is and how it works. In Radix sort, we are sorting by comparing individual digits from the last one to the first one. In essence, radix sort is like this: sort elements by the last digit. 

How to check if a String has all unique characters in Java? [Solved]

Hello guys, its been long time since I shared any interesting coding problem but the wait is over. Today, I am going to share one interesting and popular String based coding problem which you would love to solve. Today's coding challenge is to find out if a given string has all unique characters or not, for example, if given String is "Java" then your function should return false because all styles from this String are not unique. On the other hand, if the given String is "Python," then your function should return true because all characters are unique in this String. Btw, don't just jump on the solution if this is ever asked to you on Interview; instead, you should ask a couple of good questions to demonstrate your requirement gathering skill and attention for details.

5 ways to find length of String in Java - Example Tutorial

On another day, someone asked me, is there a way to find the length of String without using the length() method from java.lang.String class? I didn't ask why, because I know it might have been asked to him on Interviews. Before I explore ways to find the length of String, let's recap what does the length of String means in Java? Well, it's no different than C here, a number of characters in a String including whitespace, newlines are known as length of String. By knowing this, you can think of many approaches to calculating length e.g. getting a char array from String and counting a number of characters or many are by applying some clever tricks.

How to implement Linear Search in Java? Example Tutorial

Hello guys, earlier, I have talked about how the binary search algorithm works and shared the code to implement the binary search in Java. In that article, someone asked me about is there any other search algorithm that exists? How can you search an element in the array if it's not sorted, and you cannot use the binary search algorithm? To answer his questions, I mentioned the Linear search algorithm, which is the predecessor of binary search. Generally, it is taught before the binary search algorithm because the binary search is faster than Linear search. However, never mind, you can still learn this useful algorithm to search for an item in the array or linked list.

How to Find Square Root of a Number in Java? Example Solution

Write a program to calculate the square root of a number in Java or C++ is one of the popular coding interview questions from Programming job interviews both on tech companies like Facebook, Amazon, and investment banks like Citibank and Bank Of America, etc. The problem may look easy because you might know how to find the square root of a number but it's not. In fact, it's one of the tricky questions you would encounter in programming job interviews. The first hurdle is do you really remember how to calculate square root by hand? Many programmers don't. I know they have learned it past but when you ask them to calculate square root by hand, many won't remember the algorithm they have learned in school or college.

Counting Sort Algorithm in Java? Example Tutorial

Hello guys, in our last article, we looked at the Radix Sort in Java and in this article, we will look at the counting sort in Java. If you are thinking how they are related then let me tell you that both are O(n) sorting algorithms. Yes, its possible to sort in O(n) or linear time. If you are wondering that you have so far only learned that best sorting algorithms are Quick Sort and Merge Sort who sorts an array in O(nLogN) time then you are in for surprise. Yes, there existing O(n) sorting algorithms which are faster than both Quicksort and Merge sort like Radix Sort, Counting Sort, and Bucket Sort but they have their limitation. They are not general purpose sorting algorithm and you can use this to sort only integers and it also depends upon how big is the data set and how many different numbers are in the data set. 

3 Ways to Find Duplicate Elements in an Array - Java

There are multiple ways to find duplicate elements in an array in Java and we will see three of them in this program. The solution and logic shown in this article are generic and apply to an array of any type e.g. String array or integer array or array of any object. One of the most common ways to find duplicates is by using the brute force method, which compares each element of the array to every other element. This solution has the time complexity of O(n^2) and only exists for academic purposes. You shouldn't be using this solution in the real world.

How to sort an Array in Java? Ascending and Descending Order Example

As a Java programmer, quite often you would need to sort array in Java luckily java.util.Arrays class provides several utility methods to sort an array in Java. You can sort different types of array in Java like array of primitive data types, object or int, String, etc. Arrays are in java.util package and exposed all sorting related methods as static utility functions. you can access sort() as Arrays.sort() and just pass your array and it will sort that array object by comparing them in the order implemented in the compareTo() method if the class implements Comparable interface. 

How to loop through an Array in Java? Example Tutorial

Hello there, If you want to loop over an array in Java but not sure how to do that then you have come to the right place. Earlier, I have shared many Java array tutorials and the best Java courses for beginners, and today, I am going to teach you how to iterate over an array in Java. There are multiple ways to loop over an array in Java, like you can use a for loop, an enhanced for loop, a while loop, or a do-while loop. Since while and do-while needs a condition to terminate they often depend upon the content of the array like stop when the current element is null or even or odd etc. If you just want to iterate over an array to access each element like loop over an array and print each entry then you should use either for loop or the enhanced for loop.

How to declare and initialize a List with values in Java (ArrayList/LinkedList) - Arrays.asList() Example

Hello guys, today, I am going to share with you a useful tip to initialize a List like ArrayList or LinkedList with values, which will help you a lot while writing unit tests and prototypes. Initializing a list while declaring is very convenient for quick use, but unfortunately, Java doesn't provide any programming constructs like the collection literals of Scala, but there is a trick which you can use to declare and initialize a List at the same time. This trick is also known as initializing a List with values. I have used this trick a lot while declaring list for unit testing and writing demo programs to understand an API etc and today I'll you'll also learn that.

How to implement Skip List in Java? Example Tutorial

Hello friends, we meet again today. hope you all are excited and ready for today's journey. Today, we are gonna learn something that is not very common. It is used not very common, but, if used, it is a great strength to our time complexity reduction. So, what's the wait? Let's start! So, suppose we have a linked list with us which has 10 million records. Now, for searching a particular node, the time taken would be O(N). Where N is the size of the list. Similarly, the time taken for deletion of a Node, Insertion at a particular Node will also take O(N) time. Can we reduce it?

How to find If Linked List Contains Loop or Cycle in Java? Example Solution

Write a Java program to check if a linked list is circular or cyclic,  and how do you find if a linked list contains loop or cycles in Java are some common linked list related data structure interview questions asked in various Java Interviews. This is sometimes asked as a follow-up question of basic linked list questions like inserting an element at the beginning, middle and end of a linked list or finding the length of linked list. In order to solve linked list related algorithmic questions in Java, you need to be familiar with the concept of singly linked list, doubly linked list, and circular linked list. Until stated specifically, most questions are based on a singly linked list. For those who are not familiar with the linked list data structure, its a collection of nodes.

How to use Array in Java? Example Tutorial

The array is one of the most important data structures in any programming language, at the same time different programming languages implement and treat the array differently. Anyone who is done some programming knows the value of an array and the importance of knowing about array type, using them in their program. Together with a linked list, the array forms a set of basic data structures. Though Java offers excellent Collection API and some of the collection classes like ArrayList and  HashMap, they are internally based on the array.

Top 15 Data Structures and Algorithm Interview Questions Answers for Java Programmer

Data structures and algorithm questions are an important part of any programming job interview, be it a Java interview, a C++ interview, or any other programming language. Since data structures are core programming concepts, it's mandatory for all programmers, to know basic data structures like the stack, linked list, queue, array, tree, and graph. Though trees and graphs are on the tougher side, I still see programmers get familiar will all these. Any list of programming job interview questions is incomplete without questions from data structures and algorithms. Similarly, while going on questions from data structure you may get some programming exercise as well e.g. swapping numbers without temp variable.