Note

There are several branches in this repository:

• master: Contains skeleton tests and skeleton production code for each of the katas listed here. All the tests fail. You can use the existing code and tests to build your solution on, or you can completely replace some or all of it.
• all the others: Each kata has its own branch. If you check out the branch for a particular kata, all the code for the other katas will disappear, and you'll see a possible solution for the selected kata. All the tests pass. In all cases, there are other solutions; there may even be better solutions. The ones provided are solutions, but not the solutions.

Babysitter

A babysitter has the following pay schedule:

• $10/hr to look after children before their bedtime
• $6/hr to house-sit after bedtime
• $8/hr after midnight when work causes her to lose sleep.

Write a method or function that will accept an arrival time, a departure time, and a bedtime, and return the babysitter's earnings for the evening in dollars.

A partial hour is always charged as a whole hour; therefore arrival and departure times will always be integral. Represent all times as integers on a 12-hour clock--not as Dates or as OffsetDateTimes or anything more complicated. The earliest the babysitter can arrive is 5pm; the latest she can stay is 4am. Bedtime must never be after midnight.

Dollars in this kata will also always be integral; hence, represent them as integers--not as Doubles or BigDecimals or anything more complicated.

The first run at this kata should not include testing or handling for any error conditions, such as arrival times less than 1 or greater than 12 or bedtimes after midnight.

Closest to Zero

Test-drive a method or function to accept a list of integers and return the one that is closest to zero.

It should be an error for the list to be empty.

If two different numbers tie for distance from zero (for example, 2 and -2), always return the positive one.

Pricing

A store has the following pricing policy:

1. Buy less than $100 worth of merchandise and pay the full price.
2. Buy $100 or more, but less than $1000, and get 10% off.
3. Buy $1000 or more, and get 15% off.

According to the laws governing the store, the following taxes apply:

• Food: no tax.
• Alcohol: 7.5% sales tax + 8% "sin" tax.
• All other merchandise: 7.5% sales tax.

Discounts are calculated on sticker prices; taxes are calculated on discounted prices.

Using TDD, write a method that will accept purchased items of food, alcohol, and other, and will return the price the customer should be charged.

Triangles

Using TDD, write a method or function that accepts three numbers as the lengths of three line segments. Determine computationally which of the following cases are true:

The three segments

1. Can be joined into an equilateral triangle. (example: 3, 3, 3)
2. Can be joined into an isosceles triangle. (example: 5, 5, 3);
3. Can be joined into a right triangle. (example: 3, 4, 5);
4. Can only be joined into a triangle that is not one of the preceding cases. (example: 2, 3, 4)
5. Cannot be made into a triangle. (example: 2, 3, 5) [Warning: might look isosceles at first glance.]

The order in which the segments are supplied must not affect the result.

Word Wrap

Test-drive a function to accept a string and a line length, and return a version of the original string, possibly with newline characters inserted, such that no line in the resulting string is longer than the supplied line length.

Wherever possible, newlines should be inserted between words; they should be placed inside words only when those words are themselves longer than the permitted line length.

For the initial cut of this kata:

• Assume that the input will contain only spaces to separate words: no tabs, no newlines, no form feeds; and hyphens, commas, periods, etc. are considered to be part of the words they're embedded in.
• Assume that words will be separated by only one space: no multiple consecutive spaces.

Pencil

(Not the Red Pencil kata, but the Pencil Kata from Marion Correctional Institution)

Test-drive code to simulate an ordinary wooden graphite pencil. Run the following steps:

1. When the pencil is instructed to write a string, it returns exactly the string it was instructed to write.

2. Add simulation of a dulling point. After writing a certain number of characters, the simulated pencil goes dull and begins to return spaces instead of the characters it's instructed to write.

3. Add sharpening capability. When a pencil is sharpened, it regains full sharpness; but it can only be sharpened a certain number of times. When sharpened past the limit, it no longer regains any sharpness.

4. It requires no lead to write a space (or a tab or a carriage return or a newline). Make the pencil capable of writing an arbitrary amount of whitespace without going any duller.

5. It requires more lead to write a capital M than it does to write a period. Come up with a reasonable classification of the writeable characters so that the pencil can write more periods than capital Ms before going dull.

Scoring Tennis

Test-drive some code to keep track of the score of a single tennis game and present it as String.

The score of a tennis game has two stages.

In the first, which we will call the Absolute Stage, the two players proceed through a sequence of absolute point names: "love," "fifteen," "thirty," and "forty." During this stage, the score will be either of the form "Alice forty, Bob fifteen" if the players have different scores, or of the form "Love all" if the scores are the same.

When a player has forty and scores again, what happens depends on the other player's score. If the other player has forty as well, the game moves on to the Relative Stage. If the other player does not have forty yet, the game is over.

In the second stage, the Relative Stage, the representation of the score depends on how many points one player has relative to the other. If Alice and Bob have the same score, the representation is "Deuce." If Bob has one more point Alice, the representation is "Advantage Bob." If Alice scores two more points than Bob, the score is "Game Alice," and the game is over.

Note that the Absolute Stage cannot possibly last longer than a total of eight points, but the Relative Stage can theoretically go on forever, as long as no one ever has two points more than his opponent.

Write some code that can take a series of scores by one player or the other and produce the proper representation of the game's score at each step.

Prohibit further scoring after the game has ended.

Ranking Poker Hands

Write some code that, given two five-card poker hands, tells which hand outranks the other.

Unlike the other katas, this one provides a significant amount of pre-written testing functionality. (Note that not all these tests fail in the master branch. However, that doesn't mean we've written any production code for you.) If you choose to use this, it will have a significant effect on the way your data structures are arranged; this may affect your algorithms. Feel free to discard it and start from scratch if you don't like it.

Poker ranking references are provided in many places on the Internet, including this one.

Translating Names

Test-drive a function that will accept a camel-cased name either beginningWithALowercaseCharacter or WithAnUppercaseOne, and produce a snake-cased version of that name, like beginning_with_a_lowercase_character or with_an_uppercase_one.

Cash Register

A small shop has a standard cash register, with a drawer containing various numbers of various denominations of bills and coins. A customer arrives at the checkout counter with a shopping cart containing merchandise of a particular value and hands the cashier a cash payment, also consisting of various numbers of various denominations of bills and coins.

There are three possibilities.

• The customer does not offer enough money for the merchandise. In this case the money is returned to the customer and the contents of the cash register is unchanged.

• The customer offers more than enough money, but the contents of the cash register cannot be used to make change. In this case the money is also returned to the customer and the contents of the cash register is unchanged.

• The customer offers enough or more than enough money for the merchandise, and the cashier is able to make change from the contents of the cash register. In this case the customer's payment is added to the cash register, and the change is removed from it.

Test-drive some code that will accept a populated cash register, a number representing the value of a cart of merchandise, and a data structure representing a cash payment; will attempt to perform the indicated transaction; and will provide results including which of the three possibilities obtained and the contents of the cash register after the transaction.

Note: Make sure your algorithm can handle the situation where fifty cents of change needs to be made and the cash register contains only one quarter and five dimes. [credit: Tracy Harms]