Question

I am trying write Dijkstras Algorithm into the code I have written below. But I am unsure how to start doing this. I did review it a bit from online sources, but I am still unsure how to make it work really. I prefer to place it into the evaluate paths method. Then have the menu option call this method and it perform the sorting algorithm.

FYI. I am sorting the shortest path from City A to City B by miles and price.

Below is the code I have.

import java.io.*;
import java.util.*;

public class CityCalcultor { 
   static LinkedList<String> cities = new LinkedList<String>();
   static LinkedList<Integer> distance = new LinkedList<Integer>();
   static LinkedList<Integer> price = new LinkedList<Integer>();
    public static void main(String[] args)throws IOException 
    {
     Scanner input = new Scanner(System.in);
     String text;
     int option = 0;   
      while (true)
      {   
       System.out.println("\nWhat would you like to do:\n" +
       "1. Add a city to the system\n" +
      "2. Add a path to the system\n" +
      "3. Evalute paths\n" +
       "4. Exit\n" + "Your option: ");
       text = input.nextLine();
       option = Integer.parseInt(text);

        switch (option)
        {
         case 1: EnterCity(); break;
         case 2: EnterPath(); break;
         case 3: EvalutePaths(); break;
         case 4: return;
         default: System.out.println("ERROR INVALID INPUT");
        }
       }
      }
public static void EnterCity(){
   String c = "";
   LinkedList<String> cities = new LinkedList<String>(Arrays.asList(c));
   Scanner City = new Scanner(System.in);
   System.out.println("Please enter the city name ");
   c = City.nextLine();
   cities.add(c);
   System.out.println("City " + c + " has been added ");

}
public static void EnterPath(){
   Scanner Path = new Scanner(System.in);
   int d = 0; int p = 0;
   System.out.println("Enter the starting city ");
   System.out.println();
   System.out.println(Path.nextLine());
   System.out.println("Enter the ending city ");
   System.out.println(Path.nextLine());
   System.out.println("Enter the distance between the two cities ");
   d= Path.nextInt();
   distance.add(d);
   System.out.println("Enter the price between the two cities ");
   p = Path.nextInt();

   price.add(p);
   System.out.println("The route was sucessfully added ");


}
private static void EvalutePaths(){


}
}

Output should look like::

Shortest Route from Seattle to San Francisco is 1290 miles.

Answer 1

here is some pseudo code for Dijkstra’s algorithm, perhaps it will help..

this will set the shortest distance to each city from the starting city..

for each city
{
    settled = false
    distance = infinity
}

startingCity.distance = 0

currentCity = startingCity

while not all cities are settled
{
    for each city adjacent to the current city
    {
        newDist = distance from adjacentCity to currentCity

        if newDist < adjacentCity.distance
        {
            adjacentCity.distance = newDist
        }  
    }

    currentCity.settled = true

    currentCity = city closest to currentCity
}