# CategoryHackerRank

## HackerRank ‘String Construction’ Solution

H

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

H

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

H

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

H

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

H

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

H

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

H

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

H

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

H

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:

## HackerRank ‘Utopian Tree’ Solution

H

Short Problem Definition: The Utopian Tree goes through 2 cycles of growth every year. The first growth cycle occurs during the spring, when it doubles in height. The second growth cycle occurs during the summer, when its height increases by 1 meter.  Now, a new Utopian Tree sapling is planted at the onset of spring. Its height is 1 meter. Can you find the height of the tree after N growth cycles...