Short Problem Definition: Your teacher has given you the task to draw the structure of a staircase. Being an expert programmer, you decided to make a program for the same. You are given the height of the staircase. Link Staircase Complexity: time complexity is O(N^2) space complexity is O(1) Execution: Either fill each level with N-i empty spaces or adjust to the right. Solution: 1 2 3 4 5 6 7 8...

## HackerRank ‘String Construction’ Solution

Short Problem Definition: Amanda has a string of lowercase letters that she wants to copy to a new string. She can perform the following operations with the given costs. She can perform them any number of times to construct a new string p: Append a character to the end of string p at a cost of 1 dollar. Choose any substring of p and append it to the end of at...

## HackerRank ‘Strong Password’ Solution

Short Problem Definition: Louise joined a social networking site to stay in touch with her friends. The signup page required her to input a name and a password. However, the password must be strong. The website considers a password to be strong if it satisfies the following criteria: Its length is at least 6. It contains at least one digit. It contains at least one...

## HackerRank ‘Super Reduced String’ Solution

Short Problem Definition: Steve has a string of lowercase characters in range ascii[‘a’..’z’]. He wants to reduce the string to its shortest length by doing a series of operations. In each operation he selects a pair of adjacent lowercase letters that match, and he deletes them. For instance, the string aab could be shortened to b in one operation. Steve’s task is to...

## HackerRank ‘Taum and B’day’ Solution

Short Problem Definition: Taum is planning to celebrate the birthday of his friend Diksha. There are two types of gifts that Diksha wants from Taum: one is black and the other is white. To make her happy, Taum has to buy B number of black gifts and W number of white gifts. Link Taum and B’day Complexity: time complexity is O(1) space complexity is O(1) Execution: The cost for each present is...

## HackerRank ‘The Grid Search’ Solution

Short Problem Definition: Given a 2D array of digits, try to find the location of a given 2D pattern of digits Link The Grid Search Complexity: time complexity is O(n^2 * m^2) space complexity is O(1) Execution: There are many sophisticated 2d pattern matching algorithms out there. Just think of computer vision, robotics, gaming… The issue with most of them is, that they are rather heuristics...

## HackerRank ‘The Power Sum’ Solution

Short Problem Definition: Find the number of ways that a given integer, X , can be expressed as the sum of the Nth powers of unique, natural numbers. For example, if X = 13 and N = 2, we have to find all combinations of unique squares adding up to 13. The only solution is 2^2 + 3^2. Link The Power Sum Complexity: time complexity is O(N!) space complexity is O(1) Execution: This solution does not...

## HackerRank ‘The Time In Words’ Solution

Short Problem Definition:

Given the time in numerals we may convert it into words.

Link

The Time In Words

Complexity:

time complexity is O(?)

space complexity is O(?)

Execution:

I might have hinted at my opinion in the past: Why do “challenges” like this even exist? It requires 0 brain power, but you will spend an hour figuring out the fine details of English and fixing bugs.

Solution:

## HackerRank ‘Time Conversion’ Solution

Short Problem Definition: You are given time in AM/PM format. Convert this into a 24 hour format. Link Time Conversion Complexity: time complexity is O(?) space complexity is O(?) Execution: Transforming date formats without the use of the proper libraries is a disaster waiting to happen. Date formats are ever changing and a waste of engineering effort. Just use whatever package comes with your...

## HackerRank ‘Two Strings’ Solution

Short Problem Definition:

You are given two strings, A and B. Find if there is a substring that appears in both A and B.

Link

Two Strings

Complexity:

time complexity is O(N+M);

space complexity is O(1)

Execution:

At first sight this seems like a longest common substring problem. It is actually much easier. You just need to find out if there are two equal letters in both strings A and B.

Solution: