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Question: Given an integer N, convert it into a string of words. Input: N = 345 Output: three hundred forty five This is one of the most common problems that we come across in out daily lives. We need to input a number from the user and print it in words. First, we perform a number of checks on the input string. If it is in any way invalid, the result is the empty string (“”). Next, we take note of whether or not the string begins with a ‘-‘. …

In this post, I would try to implement the following string-related algorithm questions. I would like to implement these using Java and try to make additional comments which I think that are useful for understanding the implementations of some type of data structures in Java programming language. Non Repeated Characters in String : Return the unique characters in a given letter. Anagram Strings : Given two strings, check if they’re anagrams or not. Two strings are anagrams if they are written using the same exact letters, ignoring space, punctuation and …

Question: Given an integer N, find the prime numbers in that range from 1 to N. Input: N = 25Output: 2, 3, 5, 7, 11, 13, 17, 19, 23 We discussed the basic approaches to find the first N prime numbers in these posts Find the first N prime numbers (Method 1) Find the first N prime numbers (Method 2) It is advised that you go through the above posts to get a basic understanding of the approach that we have used to determine the prime numbers. Now lets analyze …

Question: Given an integer N, find the prime numbers in that range from 1 to N. Input: N = 25 Output: 2, 3, 5, 7, 11, 13, 17, 19, 23 We discussed the most basic approach to find the first N prime numbers in this post. Find the first N prime numbers. (Method 1) Please go through the post if you are not familiar with the naive methods. They are necessary to learn how the code can be optimized further. So let us try to further optimize the previously discussed …

Question: Given an integer N, find the prime numbers in that range from 1 to N. Input: N = 25 Output: 2, 3, 5, 7, 11, 13, 17, 19, 23 Today let us discuss about a very common but very interesting problem “To find prime numbers in first N Natural numbers “. I will be taking here a very specific approach of first giving definition of prime numbers , using that definition to derive the algorithm, and then using different properties or results that can be further applied to our …

Question: You are given two axis-aligned rectangles. You have to determine if these rectangles overlap each other or not. Rectangle 1 : P1 (x, y), P2 (x,y) Rectangle 2 : P3 (x,y), P4 (x,y) In this problem statement, we are given co-ordinates for 2 rectangles and we have to determine if they overlap or not. In a way we can say that our use case looks like this. At the first glance, the problem seems to look very complicated. If you are coming up with a complicated set of conditionals, …

Question: Given an unsigned Integer, you need to reverse its bits. There are several methods of reversing the bits of an unsigned integer. Here, we devise an algorithm using the XOR swap trick. Hint: How do you swap the ith bit with the jth bit? Try to figure out if you could use the XOR operation to do it. The XOR swap trick: Reversing bits could be done by swapping the n/2 least significant bits with its most significant bits. The trick is to implement a function called swapBits(i, j), …

Question: Given an Integer, you need to determine if it is a palindrome or not. You should not use any extra space in the process. Input: 121 Output: Palindrome At the first go, the problems seems very easy to solve. We just need to reverse the number and check if it remains the same. Right? Don’t be deceived by this problem which seems too easy. Also note the restriction of doing it without extra space. We also need to think of a generic solution that is not language/platform specific. First, …

Here we will discuss the easiest and most simple way to change case of alphabets. Hint : We will be using bit hacks. Often during our programming needs we need to change the case of alphabets. This can be a problem requirement or simply our need to solve the question. There are several ways to do it, but what can be more beautiful than using bit hacks for the same. We discusses some of the BIT Hacks in these posts:- Low Level Bit Hacks Some advanced Bit Hacks Here I …

Here we shall discuss some high level Bit hacks that if used cleverly can really speed up your program execution time. We discussed some of the basic hacks in this post:- Low level bit hacks you must know. Please go through the post to get a little understanding of how the things work. Smart learners are anyways welcome to proceed. ;-) BIT HACK 6: Turn off the rightmost 1-bit. Now it finally gets more interesting!!! Bit hacks #1 – #5 were kind of boring to be honest. This bit hack …