Java Program to print pyramid pattern of stars and numbers

You can print Pyramid pattern of stars or numbers using loops and print methods in Java. There are two print method you need to know, System.out.print() and System.out.println(), the difference between print() and println() is that println adds a new line character at the end i.e. it appends \n automatically. which means next time you write something will begin at the new line. On the other hand, if you use print() then the text is appended to the same line. By using these two methods, you can print any kind of pattern in Java program e.g. pattern involving multiple stars in one line, a pattern involving stars at different lines, pyramid of numbers, a pyramid of stars, inverted pyramid pattern of numbers, stars and alphabets, and so on.

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How to find square root of a number in Java - Algorithm Interview question

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.

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How to check if two Rectangle Overlap in Java - Algorithm

Can you write a Java program to check if two rectangles are overlapping with each other or not? is one of the frequently asked coding questions on tech giants like Facebook, Amazon, Microsoft and others. This is also a kind of problem where it's easy to find opposite or negative conditions e.g. when rectangles are not overlapping and then inverting the result to prove that rectangles are colliding with each other. I first heard about this problem from one of my friend who was on Android game development space. He was asked to write an algorithm to find if given rectangles are intersecting or not. He was given the choice to implement the algorithm in any programming language e.g. Java, C, C++ or even pseudo code was fine, so don't worry about language here, it's more about algorithm and logic. He is a genius so he came successful from that interview, impressing the interviewer, talking about efficiency and accuracy of the algorithm as well.

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How to find the 3rd element from end in linked list in Java

The problem to find the 3rd element from the end in a singly linked list or nth node from the tail is one of the tricky but frequently asked linked list problems in programming job interviews. The challenge here is to solve the problem in just one pass, i.e. you can not traverse the linked list again and you cannot traverse backward because it's a singly linked list. If you have practiced some linked list problems e.g. finding length, inserting elements, or deleting elements then you should be familiar with traversal. Here, we'll use the same algorithm which we have used to find the middle element of linked list in one pass. The algorithm is also known as tortoise and hare algorithm because of the speed of two pointers used by the algorithm to traverse the singly linked list.

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Printing Largest and Smallest of N numbers without using Array in Java

One of the common programming questions is, how do you find the largest and smallest number in N numbers without using arrays in Java? Can you write a program to solve this problem? Well, it's very similar to the problem we have seen before, find the largest and smallest of 3 integers. You can use the same approach and generalize it for N numbers. All you need to do is start with largest as Integer.MIN_VALUE and smallest number as Integer.MAX_VALUE and loop through N numbers. At each iteration, compare the number with the largest and smallest number, if the current number is larger than largest than its a new largest and if the current number is smaller than smallest than its a new smallest number.

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How to Remove Duplicate Characters from String in Java

This week's coding exercise is to remove duplicate characters from String in Java. For example, if given String is "aaaaaa" then output should be "a", because rest of  the "a" are duplicates. Similarly, if the input is "abcd" then output should also be "abcd" because there is no duplicate character in this String.  By the way, you can not use any third-party library or Java API method to solve this problem, you need to develop your own logic or algorithm and then write code to implement that algorithm. This is one of the interesting problems from Java coding interviews and you can use this program to weed out Java programmers who cannot write code. This problem is much better than Fizzbuzz because it requires more logic and coding than solving Fizzbuzz.

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How to reverse an ArrayList in place in Java - Example

You can reverse an ArrayList in place in Java by using the same algorithm we have used to reverse an array in place in Java. If you have already solved that problem then It's a no-brainer because ArrayList is nothing but a dynamic array, which can resize itself. All elements of an array are stored in the internal array itself. By the way, if you need to reverse an ArrayList then you should be using the Collections.reverse() method provided by Java Collection framework. It's generic method, so you can not only reverse an ArrayList but also Vector, LinkedList, CopyOnWriteArrayList, or any other List implementation. Though, worth noting is that this method internally uses a ListIterator for reversing the list, which might not be as efficient as our algorithm.

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How to Reverse an ArrayList in Java using Recursion - Example Tutorial

If you ever need to reverse a List in Java e.g. ArrayList or LinkedList, you should always use the Collections.reverse() method. It's safe and tested and probably perform better than the first version of the method you write to reverse an ArrayList in Java. It's also one of the recommended best practice to prefer library method instead of writing your own, as advised by great Joshua Bloch in Effective Java. There are so many benefits of using library method e.g it was written by experts, thoroughly and open source tested and more actively maintained. Anyway, if you have been asked to write a function to reverse a List using recursion in Java, may be as part of your homework, assignment or during an interview, then you are in the right place. In this tutorial, I'll show you how to reverse an ArrayList of String using recursion. You can use this technique to reverse any type of List e.g. List of Integer, List of String or List of your own custom objects.

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How to Reverse a String in place in Java - Example

It's possible to reverse a String in place by using a StringBuilder. Since String is Immutable in Java, it's not possible to reverse the same String, but you can minimize the number of intermediate String objects by using StringBuilder or StringBuffer, which are mutable. The algorithm to reverse the String in place is similar to the algorithm we have used earlier to reverse an array in place. You need to traverse the String from one end, swapping characters at another end until you reach the middle of the String. At the point characters in your String is reversed. This algorithm only requires one extra character of memory to facilitate the swapping of characters. The time complexity of this algorithm is O(n/2) i.e. O(n) where n is the length of String.

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Top 20 Amazon and Google Programming Interview Questions

Hello, In this article I am going to sharing some frequently asked programming job interviews from technical giants and startups. If you are going for a programming job interview with Microsoft, Google or Amazon, you better be prepared for  all kinds of questions. These companies are known to ask tough questions, tricky puzzles and lots of data structure and algorithm questions. Since it's hard to prepare all these in a short time, it makes sense to at least have a good idea of frequently asked programming questions in Microsoft, Google or Amazon. There are a lot of questions spread across the internet and if you are good in googling (not to mention, an important surviving skill in programming job), you can get tons of questions asked in these companies, or you can read Cracking the coding interview book, which contains 150+ programming questions and their solutions.

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