The given program is used to modify weight in the nine tails problem is as follows:

Program:

Edge.java: Refer book from chapter 28 – Listing 28.1.

Graph.java: Refer book from chapter 28 – Listing 28.3.

UnweightedGraph.java: Refer book from chapter 28 – Listing 28.4.

WeightedGraph.java: Refer book from chapter 29 – Listing 29.2.

WeightedEdge.java: Refer book from chapter 29 – Listing 29.1.

NineTailModel.java: Refer book from chapter – Listing 28.13.

Test.java:

//import the required statement

import java.util.ArrayList;

import java.util.List;

import java.util.Scanner;

//definition of "Test" class

public class Test

{

//main method

public static void main(String[] args)

{

//memory allocation

new Test();

}

//definition of "Test"

public Test()

{

// get the input from the user

System.out.print("Enter an initial nine coin H’s and T's: ");

Scanner input = new Scanner(System.in);

String s = input.nextLine();

//declare the variable

char[] initialNode = s.toCharArray();

//create an object

ModifiedWeightedNineTailModel model = new ModifiedWeightedNineTailModel();

//create an ArrayList

java.util.List<Integer> path =

model.getShortestPath (NineTailModel.getIndex(initialNode));

//display the steps to flip the coin

System.out.println("The steps to flip the coins are ");

for (int i = 0; i < path.size(); i++)

NineTailModel.printNode(

NineTailModel.getNode (path.get(i).intValue()));

//display the number of flips

System.out.println("The number of flips is " +

model.getNumberOfFlips (NineTailModel.getIndex(initialNode)));

}

//definition of "ModifiedWeightedNineTailModel"

public static class ModifiedWeightedNineTailModel extends NineTailModel

{

//constructor

public ModifiedWeightedNineTailModel()

{

// create edges

List<WeightedEdge> edges = getEdges();

// create a graph

WeightedGraph<Integer> graph = new WeightedGraph<Integer>(

edges, NUMBER_OF_NODES);

/* obtain a BSF tree rooted at the target node*/

tree = graph.getShortestPath(511);

}

//definition of "getEdge" method

private List<WeightedEdge> getEdges()

{

// create an ArrayList

List<WeightedEdge> edges = new ArrayList<WeightedEdge>();

//check the condition

for (int u = 0; u < NUMBER_OF_NODES; u++)

{

//check the condition

for (int k = 0; k < 9; k++)

{

// get the node for vertex u

char[] node = getNode(u);

//check the condition

if (node[k] == 'H')

{

/*call the "getFlippedNode" method*/

int v = getFlippedNode(node, k);

int numberOfFlips = getNumberOfFlips(u, v);

/* add edge for a legal move from node u to node v*/

edges.add(new WeightedEdge(v, u, numberOfFlips));

}

}

}

//return statement

return edges;

}

//definition of "getNumberOfFlips" method

private static int getNumberOfFlips(int u, int v)

{

//declare the variables

char[] node1 = getNode(u);

char[] node2 = getNode(v);

int count = 0;

//check the condition

for (int i = 0; i < node1.length; i++)

//check the condition

if (node1[i] != node2[i]) count++;

//return statement

return 3 * count;

}

//definition of "getNumberOfFlips" method

public int getNumberOfFlips(int u)

{

//return statement

return (int)((WeightedGraph<Integer>.ShortestPathTree)tree).getCost(u);

}

}

}

Enter an initial nine coin H’s and T's: HHHTTTHHH

The steps to flip the coins are

HHH

TTT

HHH

HHH

THT

TTT

TTT

TTT

TTT

The number of flips is 24