private void recPaths(double maxCost, double currCost, City currCity) {
// Backtrack if above max cost
if (currCost > maxCost) {
marked[currCity.id() - 1] = false;
return;
}
// Print current path before continuing along routes
if (edgeTo[currCity.id() - 1] != null) {
System.out.printf("Cost: %.0f Path (reversed): ", currCost);
City temp = currCity;
for (Route r = edgeTo[temp.id() - 1]; r != null; r = edgeTo[temp.id() - 1]) {
System.out.printf("%s %.0f ", temp, r.price());
temp = r.other(temp);
}
System.out.println(temp);
}
// Recursion
marked[currCity.id() - 1] = true;
for (Route r : adj[currCity.id() - 1]) {
City other = r.other(currCity);
// Don't follow route if other city already in path
if (!marked[other.id() - 1]) {
edgeTo[other.id() - 1] = r;
recPaths(maxCost, currCost + r.price(), other);
}
}
// traversed all paths from currCity, backtrack to previous city
marked[currCity.id() - 1] = false;
}
// relax edge e and update pq if changed
private void relaxC(Route r, int v) {
City city2 = r.other(cities[v]);
int w = city2.id() - 1;
if (costTo[w] > costTo[v] + r.price()) {
costTo[w] = costTo[v] + r.price();
edgeTo[w] = r;
if (costPQ.contains(w)) costPQ.change(w, costTo[w]);
else costPQ.insert(w, costTo[w]);
}
}
// Option 4
public void shortestByCost(String c1, String c2) {
System.out.println("SHORTEST COST PATH from " + c1 + " to " + c2);
System.out.println("--------------------------------------------------------");
City city1 = null;
City city2 = null;
for (int i = 0; i < numCities; i++) {
if (cities[i].name().equals(c1)) {
city1 = cities[i];
}
if (cities[i].name().equals(c2)) {
city2 = cities[i];
}
}
if (c1.equals(c2) || city1 == null || city2 == null) {
System.out.println("Invalid city choice(s)");
return;
}
costTo = new double[numCities];
edgeTo = new Route[numCities];
for (int i = 0; i < numCities; i++) costTo[i] = Double.POSITIVE_INFINITY;
costTo[city1.id() - 1] = 0;
// relax vertices in order of distance from s
costPQ = new IndexMinPQ<Double>(numCities);
costPQ.insert(city1.id() - 1, costTo[city1.id() - 1]);
while (!costPQ.isEmpty()) {
int v = costPQ.delMin();
for (Route r : adj[v]) relaxC(r, v);
}
if (costTo[city2.id() - 1] == Double.POSITIVE_INFINITY) {
System.out.println("No path");
return;
}
System.out.printf("Shortest cost from %s to %s is %.2f\n", c1, c2, costTo[city2.id() - 1]);
System.out.println("Path with edges (in reverse order):");
City currCity = city2;
for (Route r = edgeTo[city2.id() - 1]; r != null; r = edgeTo[currCity.id() - 1]) {
System.out.print(currCity + " " + r.price() + " ");
currCity = r.other(currCity);
}
System.out.println(currCity);
}