• Tandem Bicycle [Easy]
  • Method 1

Tandem Bicycle [Easy]

• 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

Hints

Method 1

【O(nlog(n))time∣O(1)space】

package Greedy;

import java.util.Arrays;

/**
 * @author zhengstars
 * @date 2023/05/06
 */
public class TandemBicycle2 {
    public int tandemBicycle(int[] redShirtSpeeds, int[] blueShirtSpeeds, boolean fastest) {
        // Sort the two arrays
        Arrays.sort(redShirtSpeeds);
        Arrays.sort(blueShirtSpeeds);

        // Initialize the total speed
        int total = 0;

        // Determine the direction of pointer movement
        int direction =  fastest ? -1 : 1;

        // Set the starting position of the red-shirt pointer based on the input parameter
        int redPointer = fastest ? redShirtSpeeds.length - 1 : 0;

        // The starting position of the blue-shirt pointer is 0
        int bluePointer = 0;

        // Traverse the speed list of blue-shirt riders
        while (bluePointer < blueShirtSpeeds.length) {
            // Choose the faster of the two riders and add their speed to the total speed
            total += Math.max(redShirtSpeeds[redPointer], blueShirtSpeeds[bluePointer++]);
            // Move the pointer one step in the specified direction
            redPointer += direction;
        }

        // Return the total speed
        return total;
    }
}