Implemented heuristic

src/search/EightPuzzleNode.java

@@ -28,10 +28,10 @@ public class EightPuzzleNode extends Node<int[][]>
     {
         final var successors = new ArrayList<Node<int[][]>>();
         final var emptyPosition = Objects.requireNonNull(detectEmptyPosition());
-        final int x = emptyPosition.getX();
-        final int y = emptyPosition.getY();
+        final var x = emptyPosition.getX();
+        final var y = emptyPosition.getY();
 
-        for (final Direction dir : Direction.values())
+        for (final var dir : Direction.values())
         {
             final var newState = copyOfState();
 
@@ -50,7 +50,6 @@ public class EightPuzzleNode extends Node<int[][]>
                 {
                     successors.add(successor);
                 }
-
             }
             catch (final ArrayIndexOutOfBoundsException ignored)
             {
@@ -63,9 +62,9 @@ public class EightPuzzleNode extends Node<int[][]>
     @Override
     public String toString()
     {
-        final StringBuilder builder = new StringBuilder();
+        final var builder = new StringBuilder();
 
-        for (final int[] row : super.value)
+        for (final var row : super.value)
         {
             builder.append(Arrays.toString(row)).append("\n");
         }
@@ -80,9 +79,9 @@ public class EightPuzzleNode extends Node<int[][]>
             return false;
         }
 
-        for (int row = 0; row < super.value.length; row++)
+        for (var row = 0; row < super.value.length; row++)
         {
-            for (int col = 0; col < super.value[row].length; col++)
+            for (var col = 0; col < super.value[row].length; col++)
             {
                 if (super.value[row][col] != node.value[row][col])
                 {
@@ -96,9 +95,9 @@ public class EightPuzzleNode extends Node<int[][]>
 
     private IntPair detectEmptyPosition()
     {
-        for (int row = 0; row < super.value.length; row++)
+        for (var row = 0; row < super.value.length; row++)
         {
-            for (int col = 0; col < super.value[row].length; col++)
+            for (var col = 0; col < super.value[row].length; col++)
             {
                 if (super.value[row][col] == 0)
                 {
@@ -114,7 +113,7 @@ public class EightPuzzleNode extends Node<int[][]>
     {
         final var copy = new int[3][3];
 
-        for (int y = 0; y < copy.length; y++)
+        for (var y = 0; y < copy.length; y++)
         {
             System.arraycopy(super.value[y], 0, copy[y], 0, copy.length);
         }
@@ -124,15 +123,9 @@ public class EightPuzzleNode extends Node<int[][]>
 
     private EightPuzzleNode swapStateField(final int[][] newState, final IntPair emptyPos, final IntPair posToSwap)
     {
-        final int posToSwapX = posToSwap.getX();
-        final int postToSwapY = posToSwap.getY();
-        final int emptyX = emptyPos.getX();
-        final int emptyY = emptyPos.getY();
-        final int tmp;
-
-        tmp = newState[postToSwapY][posToSwapX];
-        newState[postToSwapY][posToSwapX] = newState[emptyY][emptyX];
-        newState[emptyY][emptyX] = tmp;
+        final var tmp = newState[posToSwap.getY()][posToSwap.getX()];
+        newState[posToSwap.getY()][posToSwap.getX()] = newState[emptyPos.getY()][emptyPos.getX()];
+        newState[emptyPos.getY()][emptyPos.getX()] = tmp;
 
         return new EightPuzzleNode(newState, this);
     }
@@ -162,6 +155,5 @@ public class EightPuzzleNode extends Node<int[][]>
     private enum Direction
     {
         TOP, RIGHT, DOWN, LEFT
-
     }
 }

src/search/Node.java

@@ -1,6 +1,9 @@
 package search;
 
+import search.heuristic.Heuristic;
+
 import java.util.List;
+import java.util.Objects;
 
 public abstract class Node<T>
 {
@@ -14,7 +17,7 @@ public abstract class Node<T>
 
     protected Node(final T value, final Node<T> parent)
     {
-        this.value = value;
+        this.value = Objects.requireNonNull(value);
         this.parent = parent;
     }
 
@@ -28,6 +31,6 @@ public abstract class Node<T>
         return this.parent;
     }
 
-    public abstract boolean isTargetReached(Node<T> target);
+    public abstract boolean isTargetReached(final Node<T> target);
     public abstract List<Node<T>> generateSuccessors();
 }

src/search/heuristic/AStar.java

@@ -1,5 +1,39 @@
 package search.heuristic;
 
-public class AStar
+import search.Node;
+
+import java.util.Comparator;
+import java.util.PriorityQueue;
+
+public class AStar<T>
 {
+    private final Heuristic<T> heuristicFunction;
+
+    public AStar(final Heuristic<T> heuristicFunction)
+    {
+        this.heuristicFunction = heuristicFunction;
+    }
+
+    public Node<T> heuristicSearch(final Node<T> start, final Node<T> target)
+    {
+        final var nodes = new PriorityQueue<Node<T>>(Comparator.comparingInt(node -> heuristicFunction.heuristic(node, target)));
+        nodes.add(start);
+
+        while (true)
+        {
+            if (nodes.isEmpty())
+            {
+                return null;
+            }
+
+            final var node = nodes.poll();
+
+            if (node.isTargetReached(target))
+            {
+                return node;
+            }
+
+            nodes.addAll(node.generateSuccessors());
+        }
+    }
 }

src/search/heuristic/Heuristic.java

@@ -0,0 +1,8 @@
+package search.heuristic;
+
+import search.Node;
+
+public interface Heuristic<T>
+{
+    int heuristic(Node<T> node, Node<T> target);
+}

src/search/uninformed/breadthfirstsearch/BreadthFirstSearch.java

@@ -11,7 +11,7 @@ public class BreadthFirstSearch
     {
         final var newNodes = new ArrayList<Node<T>>();
 
-        for (final Node<T> node : nodes)
+        for (final var node : nodes)
         {
             if (node.isTargetReached(target))
             {

src/search/uninformed/iterativedeepening/IterativeDeepening.java

@@ -6,7 +6,7 @@ public class IterativeDeepening
 {
     public <T> Node<T> iterativeDeepening(final Node<T> node, final Node<T> target)
     {
-        int lowBarrier = 0;
+        var lowBarrier = 0;
 
         Node<T> resultNode;
 

test/search/heuristic/AStarTest.java

@@ -1,8 +1,80 @@
 package search.heuristic;
 
+import org.junit.jupiter.api.Test;
+import search.EightPuzzleNode;
+import search.Node;
+
 import static org.junit.jupiter.api.Assertions.*;
+import static search.SearchTestUtils.printSolution;
 
 class AStarTest
 {
+    @Test
+    void shouldReturnCorrectTargetCubekNodeHeuristik1()
+    {
+        final int[][] state = {
+                {3, 5, 0},
+                {1, 2, 6},
+                {4, 7, 8}
+        };
+        final var root = new EightPuzzleNode(state);
 
+        final int[][] targetState = {
+                {1, 2, 3},
+                {4, 5, 6},
+                {7, 8, 0}
+        };
+        final var expected = new EightPuzzleNode(targetState);
+
+        final var actual = new AStar<>(this::h1).heuristicSearch(root, expected);
+
+        printSolution(actual);
+    }
+
+    @Test
+    void shouldReturnCorrectTargetCubekNodeHeuristic2()
+    {
+        final int[][] state = {
+                {2, 0, 4},
+                {6, 7, 1},
+                {8, 5, 3}
+        };
+        final var root = new EightPuzzleNode(state);
+
+        final int[][] targetState = {
+                {1, 2, 3},
+                {4, 5, 6},
+                {7, 8, 0}
+        };
+        final var expected = new EightPuzzleNode(targetState);
+
+        final var actual = new AStar<>(this::h2).heuristicSearch(root, expected);
+
+        printSolution(actual);
+    }
+
+    private int h1(final Node<int[][]> node, final Node<int[][]> target)
+    {
+        final var value = node.getValue();
+        final var targetValue = target.getValue();
+        var counter = 0;
+
+        for (var row = 0; row < value.length; row++)
+        {
+            for (var col = 0; col < value[row].length; col++)
+            {
+                if (value[row][col] != targetValue[row][col])
+                {
+                    counter++;
+                }
+            }
+        }
+
+        return counter;
+    }
+
+    private int h2(final Node<int[][]> node, final Node<int[][]> target)
+    {
+        return 0;
+    }
 }