// finds the best tour possible using the branch and bound method of attack
// For an example of what to return, see DefaultSolver.solve() method.
public Problem solve()
{
Stopwatch timer = new Stopwatch();
timer.Start();
State beginningState = new State(cityData.size);
SolverHelper.initializeState(beginningState, cityData);
this.q.Enqueue(beginningState);
Problem determineBSSFProblem = SolverHelper.clone(cityData);
this.cityData.bssf = GreedySolver.solve(determineBSSFProblem).bssf;
while (q.Count > 0)
{
recur(q.Dequeue());
//Clear out any states that have a BSSF less than
//that of the current
}
timer.Stop();
cityData.timeElasped = timer.Elapsed;
return(cityData);
}
public TSPSolution(City[] cities, List <int> cityOrder, double costOfRoute)
{
// From the list of city indexes, create the list of cities
route = new List <City>(cityOrder.Count);
foreach (int i in cityOrder)
{
City temp = SolverHelper.clone(cities[i]);
route.Add(temp);
}
this.costOfRoute = costOfRoute;
}
private void recur(State state)
{
// This is a leaf
// All cities have been visited; finish and return
if (state.getCitiesVisited() == cityData.size - 1)
{
// The path to the last city is blocked
if (state.matrix[state.currCityIndex, state.cityOfOriginIndex]
== SolverHelper.SPACE_PLACEHOLDER)
{
return;
}
state.addCity(state.currCityIndex);
// Since we've hit a leaf node, we've found another possible solution
cityData.solutions++;
// Add the last hop to the lower bound to get the cost of the complete cycle
state.lowerBound += state.matrix[state.currCityIndex, state.cityOfOriginIndex];
// Check to see if this route is smaller than the current BSSF
// If so, replace the current BSSF
if (state.lowerBound < cityData.bssf.costOfRoute)
{
cityData.bssf = new TSPSolution(cityData.cities, state.cityOrder, state.lowerBound);
}
return;
}
state.addCity(state.currCityIndex);
for (int j = 1; j < state.matrix.GetLength(1); j++)
{
//Console.WriteLine(state.currCityIndex + " " + j);
//state.printState();
double currDistVal = state.matrix[state.currCityIndex, j];
if (currDistVal != SolverHelper.SPACE_PLACEHOLDER &&
state.lowerBound + currDistVal < cityData.bssf.costOfRoute)
{
State childState = SolverHelper.clone(state);
// add [i,j]
childState.lowerBound += currDistVal;
// Blank out the appropriate values with the placeholder
SolverHelper.blankOut(childState, j);
//childState.printState();
// reduce
SolverHelper.reduce(childState);
childState.currCityIndex = j;
if (childState.lowerBound < cityData.bssf.costOfRoute)
{
q.Enqueue(childState);
}
}
}
}
