Little Bobby loves chocolate. He frequently goes to his favorite 5 & 10 store, Penny Auntie, to buy them. They are having a promotion at Penny Auntie. If Bobby saves enough wrappers, he can turn them in for a free chocolate.

For example, Bobby has n = 15 to spend on bars of chocolate that cost c = 3 each. He can turn in m = 2 wrappers to receive another bar. Initially, he buys 5 bars and has 5 wrappers after eating them. He turns in 4 of them, leaving him with 1, for 2 more bars. After eating those two, he has 3 wrappers, turns in 2 leaving him with 1 wrapper and his new bar. Once he eats that one, he has 2 wrappers and turns them in for another bar. After eating that one, he only has 1 wrapper, and his feast ends. Overall, he has eaten 5 + 2 + 1 + 1 = 9 bars.

John Watson knows of an operation called a right circular rotation on an array of integers. One rotation operation moves the last array element to the first position and shifts all remaining elements right one. To test Sherlock’s abilities, Watson provides Sherlock with an array of integers. Sherlock is to perform the rotation operation a number of times then determine the value of the element at a given position.

For each array, perform a number of right circular rotations and return the value of the element at a given index.

For example, array a = [3,4,5], number of rotations, k = 2 and indices to check, m = [1,2].

First we perform the two rotations:

[3,4,5] -> [5,3,4] -> [4,5,3]

Now return the values from the zero-based indices and as indicated in the array.

a[1] = 5

a[2] = 3

We define a magic square to be an n X n matrix of distinct positive integers from 1 to n² where the sum of any row, column, or diagonal of length n is always equal to the same number: the magic constant.

You will be given a 3 X 3 matrix s of integers in the inclusive range [1,9]. We can convert any digit a to any other digit b in the range [1,9] at cost of |a - b|. Given s, convert it into a magic square at minimal cost. Print this cost on a new line.

Note: The resulting magic square must contain distinct integers in the inclusive range [1,9].

For example, we start with the following matrix s:

1
2
3

5 3 4
1 5 8
6 4 2

We can convert it to the following magic square:

1
2
3

8 3 4
1 5 9
6 7 2

This took three replacements at a cost of |5 - 8| + |8 - 9| + |4 - 7| = 7.

Alice is playing an arcade game and wants to climb to the top of the leaderboard and wants to track her ranking. The game uses Dense Ranking, so its leaderboard works like this:

• The player with the highest score is ranked number 1 on the leaderboard.
• Players who have equal scores receive the same ranking number, and the next player(s) receive the immediately following ranking number.

For example, the four players on the leaderboard have high scores of 100, 90, 90, and 80. Those players will have ranks 1, 2, 2, and 3, respectively. If Alice’s scores are 70, 80 and 105, her rankings after each game are 4^th, 3^rd and 1^st.

Consider an array of numeric strings where each string is a positive number with anywhere from 1 to 10⁶ digits. Sort the array’s elements in non-decreasing, or ascending order of their integer values and print each element of the sorted array on a new line.

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 delete as many characters as possible using this method and print the resulting string. If the final string is empty, print Empty String

About Tutorial Challenges

Many of the challenges on HackerRank are difficult and assume that you already know the relevant algorithms. These tutorial challenges are different. They break down algorithmic concepts into smaller challenges so that you can learn the algorithm by solving them. They are intended for those who already know some programming, however. You could be a student majoring in computer science, a self-taught programmer, or an experienced developer who wants an active algorithms review. Here’s a great place to learn by doing!

The first series of challenges covers sorting. They are listed below:

Your local library needs your help! Given the expected and actual return dates for a library book, create a program that calculates the fine (if any). The fee structure is as follows:

1. If the book is returned on or before the expected return date, no fine will be charged (i.e.: fine = 0).
2. If the book is returned after the expected return day but still within the same calendar month and year as the expected return date, fine = 15 Hackos X (the number of days late).
3. If the book is returned after the expected return month but still within the same calendar year as the expected return date, the fine = 500 Hackos X (the number of days late).
4. If the book is returned after the calendar year in which it was expected, there is a fixed fine of 10,000 Hackos.

Charges are based only on the least precise measure of lateness. For example, whether a book is due January 1, 2017 or December 31, 2017, if it is returned January 1, 2018, that is a year late and the fine would be .

Alice wrote a sequence of words in CamelCase as a string of letters, , having the following properties:

• It is a concatenation of one or more words consisting of English letters.
• All letters in the first word are lowercase.
• For each of the subsequent words, the first letter is uppercase and rest of the letters are lowercase.

Given s, print the number of words in s on a new line.

For example, s = oneTwoThree. There are 3 words in the string.

Given a sequence of n integers, p(1),p(2),…,p(n) where each element is distinct and satisfies 1 <= p(x) <= n. For each x where 1 <= x <= n, find any integer y such that p(p(y)) = x and print the value of y on a new line.

For example, assume the sequence p = [5, 2, 1, 3, 4]. Each value of x between 1 and 5, the length of the sequence, is analyzed as follows:

1. , so p[p[4]] = 1
2. , so p[p[2]] = 2
3. , so p[p[5]] = 3
4. , so p[p[1]] = 4
5. , so p[p[3]] = 5

The values for y are [4,2,5,1,3].