Tandem Bicycle

Category: Greedy Algorithms

Difficulty: Easy

Description

A tandem bicycle is a bicycle that's operated by two people: person A and person B. Both people pedal the bicycle, but the person that pedals faster dictates the speed of the bicycle. So if person A pedals at a speed of 5, and person B pedals at a speed of 4, the tandem bicycle moves at a speed of 5 (i.e., tandemSpeed = max(speedA, speedB)).

You're given two lists of positive integers: one that contains the speeds of riders wearing red shirts and one that contains the speeds of riders wearing blue shirts. Each rider is represented by a single positive integer, which is the speed that they pedal a tandem bicycle at. Both lists have the same length, meaning that there are as many red-shirt riders as there are blue-shirt riders. Your goal is to pair every rider wearing a red shirt with a rider wearing a blue shirt to operate a tandem bicycle.

Write a function that returns the maximum possible total speed or the minimum possible total speed of all of the tandem bicycles being ridden based on an input parameter, fastest. If fastest = true, your function should return the maximum possible total speed; otherwise it should return the minimum total speed.

"Total speed" is defined as the sum of the speeds of all the tandem bicycles being ridden. For example, if there are 4 riders (2 red-shirt riders and 2 blue-shirt riders) who have speeds of 1, 3, 4, 5, and if they're paired on tandem bicycles as follows: [1, 4], [5, 3], then the total speed of these tandem bicycles is 4 + 5 = 9.

Sample Input

redShirtSpeeds = [5, 5, 3, 9, 2]
blueShirtSpeeds = [3, 6, 7, 2, 1] 
fastest = true

Sample Output

32

Optimal Space & Time Complexity

O(nlog(n)) time | O(1) space - where n is the number of tandem bicycles