Eric Normand ericnormand

Coffee shop scenario

Jill starts to order some coffee. She adds a small, dark roast. Then she adds a large medium roast with double almond syrup. She adds a medium medium roast with two soy shots (the second one by accident). She reads the price and it's too expensive. So she removes the second coffee (the one with the almond syrup). Then she realizes the third coffee has two soy shots and she removes one. The price looks good, so she submits the order.

Super Digit

This is kind of a contrived problem, but it's the kind that breeds lots of interesting implementations and tests your understanding of lower-level details. So let's do it!

You're given an integer n and an integer k. There is an integer p that is k instances of the digits of n concatenated together. For example:

Box of chocolates

You work at a chocolate shop that makes two sizes of chocolates:

Small (2 grams each)
Large (5 grams each)

When someone orders a box of chocolates, they order by total mass. It's your job to figure out how to fulfill the order using a combination of small and large chocolates to exactly hit the total mass ordered.

How many digits?

Imagine you took all the integers between n and m (exclusive, n < m) and concatenated them together. How many digits would you have? Write a function that takes two numbers and returns how many digits. Note that the numbers can get very big, so it is not possible to build the string in the general case.

Examples:

(num-digits 0 1) ;=> 0 (there are no integers between 0 and 1)
(num-digits 0 10) ;=> 9 (1, 2, 3, 4, 5, 6, 7, 8, 9)
(num-digits 9 100) ;=&gt; 180

Least common multiple

Write a function that finds the least common multiple of a collection of numbers. Remember that the least common multiple is the smallest integer that is evenly divisible by all the numbers in the collection.

Examples:

(lcm []) ;=> nil (undefined)
(lcm [10]) ;=> 10
(lcm [2 4]) ;=&gt; 4

Simplifying fractions

A harder one for this week.

Fractions are often represented in simplified form, where the numerator and denominator share only the factor 1. Write a function simplify that takes two integers (representing the numerator and denominator) and simplifies the fraction they represent, returning the two numbers.

Examples

;; the fraction 10/10

Roboto

A futuristic robot is programmed to take in a sequence of numbers. Each number is the distance to travel in a cardinal direction (north, south, east, west). It starts facing north at (0, 0), travels straight ahead by the distance given in the first number, then turns 90 degrees clockwise, now facing east. Then it repeats with the next number. Your job is to calculate where it ends up at the end of the sequence.

Examples

License plates

When you cross the border in a car, you have to abide by the local license plate regulations. (This is not true, but let's play pretend!) The order of the numbers and letters stays the same. But the groupings change from country to country.

Write a function that takes a license plate code (letters, digits, and hyphens in a string) and a group size (integer). The function should return a new string with the characters regrouped with hyphens between groups. All groups should be of the given size, except for perhaps the first, if there aren't enough characters to fill the group.

Examples

(regroup "A5-GG-B88" 3) ;=&gt; "A-5GG-B88"

Reverse words

Write a function that takes a string containing words (one or more sentences) and returns a string containing the words in reverse order.

Examples

(reverse-words "my name is Eric.") ;;=> "Eric. is my name"
(reverse-words "hello") ;;=> "hello"
(reverse-words "I love you") ;;=&gt; "you love I"

	/**
	// Using number of minutes for prep time

	mealPrep([120])
	2 // one single long dish

	mealPrep([30, 30, 30, 20])
	2 // multiple shorter dishes
	^
	I don't understand, this should take 60 minutes.