## Kth largest element in an array (Method 1)

Question: Given an unsorted array of integers and a number ‘k’. Return the kth largest element in the array. Input: arr = {3,2,1,5,6,4}, k = 2 Output: 5 Given an unsorted array of integers, you need to determine the kth largest element. By taking a first glance at the problem we can be sure of one thing. If… Read More »

## Convert a number into a string of words

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… Read More »

## Common String Algorithms

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… Read More »

## Find the first N prime numbers. (Method 3)

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 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… Read More »

## Find the first N prime numbers. (Method 2)

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… Read More »

## Find the first N prime numbers. (Method 1)

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… Read More »

## Determine if 2 rectangles overlap

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… Read More »

## Reverse bits in an unsigned integer

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… Read More »

## Check if an Integer is a palindrome without using extra space.

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… Read More »

## Easiest way to change case of alphabets

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… Read More »