Add some fun stuff

src/search/ChessKnightNode.java

@@ -0,0 +1,93 @@
+package search;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * For a Kata on codewars.com.
+ * How many moves need a knight (Springer) to get from a given start to a given end on the chessboard,
+ * e.g. a3 -> b5, the knight needs 1 move;
+ * a1 -> f1, the knight needs 3 moves
+ */
+public class ChessKnightNode extends Node<ChessKnightNode.KnightPair> {
+    public ChessKnightNode(final KnightPair state) {
+        super(state);
+    }
+
+    private ChessKnightNode(final KnightPair value, final Node<KnightPair> parent, final int heuristicCosts) {
+        super(value, parent, heuristicCosts);
+    }
+
+    @Override
+    public boolean isTargetReached(final Node<KnightPair> target) {
+        return this.valueEquals(target);
+    }
+
+    @Override
+    public List<Node<KnightPair>> generateSuccessors() {
+        final var successors = new ArrayList<Node<KnightPair>>();
+
+        for (final var dir : ChessDirections.values()) {
+            try {
+                final char newCol = (char) (super.value.col() + dir.getColChange());
+                final char newRow = (char) (super.value.row() + dir.getRowChange());
+
+                final var newState = new KnightPair(newCol, newRow);
+
+                final var successor = new ChessKnightNode(newState, this, super.heuristicCosts + 1);
+
+                if (!successor.valueEquals(this) && !successor.valueEquals(super.getParent())) {
+                    successors.add(successor);
+                }
+            } catch (final ChessKnightException ignored) {
+            }
+        }
+
+        return successors;
+    }
+
+    private boolean valueEquals(final Node<KnightPair> node) {
+        return node != null && super.value.equals(node.value);
+    }
+
+    @Override
+    public String toString() {
+        return "%c%c".formatted(super.value.col, super.value.row);
+    }
+
+    protected record KnightPair(char col, char row) {
+        public KnightPair {
+            if (col < 'a' || col > 'h') throw new ChessKnightException("Row out of bounds at index %c".formatted(col));
+            if (row < '1' || row > '8') throw new ChessKnightException("Column out of bounds at index %c".formatted(row));
+        }
+    }
+
+    protected enum ChessDirections {
+        TOP_LEFT(-1, 2), TOP_RIGHT(1, 2),
+        RIGHT_TOP(2, 1), RIGHT_BOTTOM(2, -1),
+        DOWN_RIGHT(1 ,-2), DOWN_LEFT(-1,-2),
+        LEFT_BOTTOM(-2,-1), LEFT_TOP(-2,1);
+
+        public final int colChange;
+        public final int rowChange;
+
+        ChessDirections( final int colChange, final int rowChange) {
+            this.colChange = colChange;
+            this.rowChange = rowChange;
+        }
+
+        public int getColChange() {
+            return colChange;
+        }
+
+        public int getRowChange() {
+            return rowChange;
+        }
+    }
+
+    protected static class ChessKnightException extends IndexOutOfBoundsException {
+        public ChessKnightException(final String s) {
+            super(s);
+        }
+    }
+}

test/search/ChessKnightNodeTest.java

@@ -0,0 +1,107 @@
+package search;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ChessKnightNodeTest
+{
+    @Test
+    public void shouldReturnTrueWhenTargetReached()
+    {
+        final var state = new ChessKnightNode.KnightPair('a', '1');
+
+        final var node = new ChessKnightNode(state);
+        final var target = new ChessKnightNode(state);
+
+        Assertions.assertTrue(node.isTargetReached(target));
+    }
+
+    @Test
+    public void shouldReturnFalseWhenTargetNotReached()
+    {
+        final var actualState = new ChessKnightNode.KnightPair('a', '1');
+
+        final var targetState = new ChessKnightNode.KnightPair('h', '8');
+
+        final var node = new ChessKnightNode(actualState);
+        final var target = new ChessKnightNode(targetState);
+
+        Assertions.assertFalse(node.isTargetReached(target));
+    }
+
+    @Test
+    public void shouldReturnNonEmptyListOfSuccessors()
+    {
+        final var state = new ChessKnightNode.KnightPair('a', '1');
+
+        final var node = new ChessKnightNode(state);
+        final var successors = node.generateSuccessors();
+
+        Assertions.assertFalse(successors.isEmpty());
+    }
+
+    @Test
+    public void shouldReturnCorrectSuccessorsWithMaxPossibleSuccessors()
+    {
+        final var state = new ChessKnightNode.KnightPair('f', '3');
+
+        final var node = new ChessKnightNode(state);
+        final var successors = node.generateSuccessors();
+
+        Assertions.assertEquals(8, successors.size());
+
+        final var newState1 = new ChessKnightNode.KnightPair('e', '5');
+        final var newState2 = new ChessKnightNode.KnightPair('g', '5');
+        final var newState3 = new ChessKnightNode.KnightPair('h', '4');
+        final var newState4 = new ChessKnightNode.KnightPair('h', '2');
+        final var newState5 = new ChessKnightNode.KnightPair('g', '1');
+        final var newState6 = new ChessKnightNode.KnightPair('e', '1');
+        final var newState7 = new ChessKnightNode.KnightPair('d', '2');
+        final var newState8 = new ChessKnightNode.KnightPair('d', '4');
+
+
+        Assertions.assertEquals(newState1, successors.get(0).getValue());
+        Assertions.assertEquals(newState2, successors.get(1).getValue());
+        Assertions.assertEquals(newState3, successors.get(2).getValue());
+        Assertions.assertEquals(newState4, successors.get(3).getValue());
+        Assertions.assertEquals(newState5, successors.get(4).getValue());
+        Assertions.assertEquals(newState6, successors.get(5).getValue());
+        Assertions.assertEquals(newState7, successors.get(6).getValue());
+        Assertions.assertEquals(newState8, successors.get(7).getValue());
+    }
+
+    @Test
+    public void shouldReturnCorrectSuccessorsOnEdge()
+    {
+        final var state = new ChessKnightNode.KnightPair('a', '1');
+
+        final var node = new ChessKnightNode(state);
+        final var successors = node.generateSuccessors();
+
+        Assertions.assertEquals(2, successors.size());
+
+        Assertions.assertThrows(ChessKnightNode.ChessKnightException.class,
+                () -> new ChessKnightNode.KnightPair((char) ('a' - 1), '3'));
+
+        final var newState1 = new ChessKnightNode.KnightPair('b', '3');
+        final var newState2 = new ChessKnightNode.KnightPair('c', '2');
+
+        Assertions.assertThrows(ChessKnightNode.ChessKnightException.class,
+                () -> new ChessKnightNode.KnightPair('c', '0'));
+
+        Assertions.assertThrows(ChessKnightNode.ChessKnightException.class,
+                () -> new ChessKnightNode.KnightPair('c', (char) ('0' - 1)));
+
+        Assertions.assertThrows(ChessKnightNode.ChessKnightException.class,
+                () -> new ChessKnightNode.KnightPair((char) ('a' - 1), (char) ('0' - 1)));
+
+        Assertions.assertThrows(ChessKnightNode.ChessKnightException.class,
+                () -> new ChessKnightNode.KnightPair((char) ('a' - 2), '0'));
+
+        Assertions.assertThrows(ChessKnightNode.ChessKnightException.class,
+                () -> new ChessKnightNode.KnightPair((char) ('a' - 2), '3'));
+
+        Assertions.assertEquals(newState1, successors.get(0).getValue());
+        Assertions.assertEquals(newState2, successors.get(1).getValue());
+    }
+}

test/search/ChessKnightTest.java

@@ -0,0 +1,51 @@
+package search;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import search.uninformed.breadthfirstsearch.BreadthFirstSearch;
+
+import java.util.List;
+
+import static search.SearchTestUtils.countNodes;
+import static search.SearchTestUtils.printSolution;
+
+public class ChessKnightTest
+{
+    @Test
+    public void shouldReturnOne()
+    {
+        final var state = new ChessKnightNode.KnightPair('a', '3');
+
+        final var root = new ChessKnightNode(state);
+
+        final var targetState = new ChessKnightNode.KnightPair('b', '5');
+        final var expected = new ChessKnightNode(targetState);
+
+        final var actual = new BreadthFirstSearch().breadthFirstSearch(List.of(root), expected);
+
+        printSolution(actual);
+        var nodeCount = countNodes(actual);
+        var edgeCount = nodeCount - 1;
+
+        Assertions.assertEquals(1, edgeCount);
+    }
+
+    @Test
+    public void shouldReturnThree()
+    {
+        final var state = new ChessKnightNode.KnightPair('a', '1');
+
+        final var root = new ChessKnightNode(state);
+
+        final var targetState = new ChessKnightNode.KnightPair('f', '1');
+        final var expected = new ChessKnightNode(targetState);
+
+        final var actual = new BreadthFirstSearch().breadthFirstSearch(List.of(root), expected);
+
+        printSolution(actual);
+        var nodeCount = countNodes(actual);
+        var edgeCount = nodeCount - 1;
+
+        Assertions.assertEquals(3, edgeCount);
+    }
+}

test/search/GameHelperTest.java

@@ -11,9 +11,9 @@ public class GameHelperTest
     void shouldReturnCorrectTargetWartales()
     {
         final int[][] state = {
-                {5, 8, 2},
-                {1, 7, 3},
-                {4, 0, 6}
+                {1, 8, 6},
+                {3, 2, 7},
+                {5, 4, 0}
         };
         final var root = new EightPuzzleNode(state);
 

test/search/SearchTestUtils.java

@@ -17,4 +17,18 @@ public class SearchTestUtils
 
         System.out.println("START");
     }
+
+    public static <T> int countNodes(final Node<T> targetNode)
+    {
+        var node = targetNode;
+
+        int nodeCount = 0;
+        while (node != null)
+        {
+            nodeCount++;
+            node = node.getParent();
+        }
+
+        return nodeCount;
+    }
 }