add logic to remove dead stones at the end of the game

Author: h908714124

src/main/java/com/bernd/game/Board.java

@@ -136,8 +136,8 @@ public static int[][] removeDeadStonesAround(
     if (groups.isEmpty()) {
       return board;
     }
-    Function<int[][], int[][]> remove = removeStonesIn(board.length, groups.values());
-    return remove.apply(board);
+    Function<int[][], int[][]> update = removeStonesIn(board.length, groups.values());
+    return update.apply(board);
   }
 
   private static Function<int[][], int[][]> removeStonesIn(
@@ -147,12 +147,12 @@ private static Function<int[][], int[][]> removeStonesIn(
     for (StoneGroup group : groups) {
       size += group.points().size();
     }
-    BoardUpdate result = BoardUpdate.builder(dim, size);
+    BoardUpdate update = BoardUpdate.builder(dim, size);
     for (StoneGroup group : groups) {
       for (Point point : group.points()) {
-        result.add(point, 0);
+        update.add(point, 0);
       }
     }
-    return result;
+    return update;
   }
 }

src/main/java/com/bernd/game/PointQueue.java

@@ -1,6 +1,6 @@
 package com.bernd.game;
 
-class PointQueue {
+final class PointQueue {
   private int pos;
   private final int dim;
   private final int[] queue;

src/main/java/com/bernd/game/Remove.java

@@ -0,0 +1,75 @@
+package com.bernd.game;
+
+import com.bernd.util.BoardUpdate;
+import java.util.ArrayList;
+import java.util.List;
+
+public class Remove {
+
+  private static List<Point> findGroup(
+      int[][] board,
+      int xx,
+      int yy) {
+    int color = board[yy][xx];
+    if (color == 0) {
+      return List.of();
+    }
+    int dim = board.length;
+    PointQueue pointsToCheck = PointQueue.create(dim);
+    boolean[] pointsChecked = new boolean[dim * dim];
+    pointsToCheck.offer(xx, yy);
+    List<Point> result = new ArrayList<>();
+    while (!pointsToCheck.isEmpty()) {
+      int ptId = pointsToCheck.poll();
+      int y = ptId / dim;
+      int x = ptId % dim;
+      result.add(new Point(x, y));
+      if (y > 0) {
+        int c = board[y - 1][x];
+        int bptId = (y - 1) * dim + x;
+        if (c == color && !pointsChecked[bptId]) {
+          pointsChecked[bptId] = true;
+          pointsToCheck.offer(x, y - 1);
+        }
+      }
+      if (y < dim - 1) {
+        int c = board[y + 1][x];
+        int bptId = (y + 1) * dim + x;
+        if (c == color && !pointsChecked[bptId]) {
+          pointsChecked[bptId] = true;
+          pointsToCheck.offer(x, y + 1);
+        }
+      }
+      if (x > 0) {
+        int c = board[y][x - 1];
+        int bptId = y * dim + x - 1;
+        if (c == color && !pointsChecked[bptId]) {
+          pointsChecked[bptId] = true;
+          pointsToCheck.offer(x - 1, y);
+        }
+      }
+      if (x < dim - 1) {
+        int c = board[y][x + 1];
+        int bptId = y * dim + x + 1;
+        if (c == color && !pointsChecked[bptId]) {
+          pointsChecked[bptId] = true;
+          pointsToCheck.offer(x + 1, y);
+        }
+      }
+    }
+    return result;
+  }
+
+  public static int[][] removeStonesAt(
+      int[][] board, int x, int y) {
+    List<Point> group = findGroup(board, x, y);
+    if (group.isEmpty()) {
+      return board;
+    }
+    BoardUpdate update = BoardUpdate.builder(board.length, group.size());
+    for (Point point : group) {
+      update.add(point, 0);
+    }
+    return update.apply(board);
+  }
+}

src/test/java/com/bernd/game/RemoveTest.java

@@ -0,0 +1,25 @@
+package com.bernd.game;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+class RemoveTest {
+
+  @Test
+  void testRemoveTwoStones() {
+    int[][] position = new int[][]{
+        new int[]{0, 4, 4, 0},
+        new int[]{2, 2, 2, 2},
+        new int[]{4, 4, 4, 4},
+        new int[]{0, 0, 0, 0},
+    };
+    int[][] result = Remove.removeStonesAt(position, 1, 0);
+    assertArrayEquals(new int[][]{
+        new int[]{0, 0, 0, 0},
+        new int[]{2, 2, 2, 2},
+        new int[]{4, 4, 4, 4},
+        new int[]{0, 0, 0, 0},
+    }, result);
+  }
+}