### Toy Problems

## Combination Sum

Given a set of candidate numbers (candidates) (without duplicates) and a target number (target), find all unique combinations in candidates where the candidate numbers sums to target. The same repeated number may be chosen from candidates unlimited number of times. Note: All numbers (including target) will be positive integers. The ...

Read More## ZigZag Conversion

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this

P A H N A P L S I I G Y I RAnd then read line by line: "PAHNAPLSIIGYIR"

Write the code that will take a string and make this conversion ... Read More

## Pascal's Triangle

Given a non-negative integer numRows, generate the first numRows of Pascal's triangle. In Pascal's triangle, each number is the sum of the two numbers directly above it. To build the triangle, start with "1" at the top, then continue placing numbers below it in a triangular pattern.
**Example ...**

## Hackerrank Solution: Computing the GCD

Given two integers, x and y, a recursive technique to find their GCD is the Euclidean Algorithm. The algorithm states that, for computing the GCD of two positive integers x and y, if x and y are equal, GCD(x, y) = x. Otherwise GCD(x, y) = GCD(x - y, y ...

Read More## Hackerrank Solution: Almost Sorted

Given an array with n elements, can you sort this array in ascending order using only one of the following operations?
1. Swap two elements.
2. Reverse one sub-segment.
**Input Format**
The first line contains a single integer, n, which indicates the size of the array.
The next line contains ...

## Hackerrank Solution: Simple Array Sum

Given an array of integers, can you find the sum of its elements?
**Input Format**
The first line contains an integer, N, denoting the size of the array.
The second line contains N space-separated integers representing the array's elements.
**Output Format**
Print the sum of the array's elements ...