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BidirectionalBFS.java
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BidirectionalBFS.java
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package src;
import java.util.ArrayDeque;
import java.util.ArrayList;
public class BidirectionalBFS {
private ArrayDeque<Node> frontier1 = new ArrayDeque<>(), frontier2 = new ArrayDeque<>();
private ArrayList<State> explored1 = new ArrayList<>(), explored2 = new ArrayList<>();
private State state;
private Data data;
private int NUM = 1;
private double t = 0;
private String path;
private Pair<Node, Node> mres = null;
public Result result = new Result();
public BidirectionalBFS(Data d, String path){
data = d;
state = new State(data.getROBOT(), data.getBUTTER());
this.path = path;
init();
}
private void init() {
t = System.nanoTime();
run();
t = System.nanoTime() - t;
if(mres != null)
setres(mres.getFirst(), mres.getSecond());
finish();
}
public void run(){
ArrayList<String[]> map = data.getMAP();
data.getPURCHASER();
Node root = new Node(null, 0, 0, "", state);
frontier1.add(root);
for(Point p:data.getPURCHASER()) {
for(int i=-1;i<=1;i+=2) {
Point q = p.makePoint(i, 0);
if(checkEmpty(q, map))
frontier2.add(new Node(null, 0, 0, "", new State(q, data.getPURCHASER())));
q = p.makePoint(0, i);
if(checkEmpty(q, map))
frontier2.add(new Node(null, 0, 0, "", new State(q, data.getPURCHASER())));
}
}
while (!frontier1.isEmpty() && !frontier2.isEmpty()) {
mres = expandOneLayer(frontier1, frontier2, explored1, explored2, false);
if(mres != null) return;
mres = expandOneLayer(frontier2, frontier1, explored2, explored1, true);
if(mres != null) return;
}
}
private boolean checkEmpty(Point q, ArrayList<String []> map) {
return q.check(0, 0, map.size(), map.get(0).length) && !map.get(q.getX())[q.getY()].contains("x");
}
private Pair<Node, Node> expandOneLayer(ArrayDeque<Node> f1, ArrayDeque<Node> f2, ArrayList<State> e1, ArrayList<State> e2, boolean backward) {
int dep = f1.getFirst().getCutoff();
while(!f1.isEmpty() && f1.getFirst().getCutoff() == dep) {
Node node = f1.removeFirst();
e1.add(node.getState());
for(Node child : backward ? node.predecessor(data.getMAP()):node.successor(data.getMAP())) {
NUM = NUM + 1;
if(checkExplored(child, e1) || checkFrontier(child, f1)!=null)
continue;
Node res = checkFrontier(child, f2);
if(res != null)
if(backward)
return new Pair<>(res, child);
else
return new Pair<>(child, res);
f1.add(child);
}
}
return null;
}
private boolean checkExplored(Node n, ArrayList<State> ex){
for(State e:ex)
if(e.equals(n.getState()))
return true;
return false;
}
private Node checkFrontier(Node n, ArrayDeque<Node> fr){
for(Node nd:fr)
if(nd.getState().equals(n.getState()))
return nd;
return null;
}
private void setres(Node a, Node b) {
ArrayList<Node> resNodes = new ArrayList<>();
resNodeFix(a, resNodes, true);
resNodeFix(b, resNodes, false);
result.solution = "";
for(Node n:resNodes)
result.solution += n.getOrder() + " ";
result.solution = result.solution.toUpperCase();
for(Node n:resNodes) if(n != b)
result.showMaps.add(n.getState().printMap(data.getMAP()));
result.depth = result.cost = a.getCutoff() - b.getCutoff();
}
private void finish() {
result.time = t;
result.path = path;
result.expanded = explored1.size() + explored2.size();
result.generated = NUM;
if(mres == null)
result = new Result("cant pass the butter", null, -1, -1, t, path, result.expanded, NUM);
data.output(result);
}
private void resNodeFix(Node n, ArrayList<Node> rn, boolean back) {
if(!back) rn.add(n);
if(n.getP() != null)
resNodeFix(n.getP(), rn, back);
if(back) rn.add(n);
}
}