Finished BFS-livecode.

src/Search.java

@@ -1,3 +1,5 @@
+import java.util.*;
+
 public class Search {
      /**
      * Finds the location of the nearest reachable cheese from the rat's position.
@@ -29,6 +31,75 @@ public class Search {
      * @throws HungryRatException if there is no reachable cheese
      */
     public static int[] nearestCheese(char[][] maze) throws EscapedRatException, CrowdedMazeException, HungryRatException {
-        return null;
+        int[] start = findRat(maze);
+
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(start);
+
+        boolean[][] visited = new boolean[maze.length][maze[0].length];
+
+        while (!queue.isEmpty()) {
+            int[] current = queue.poll();
+            int curR = current[0];
+            int curC = current[1];
+
+            if (maze[curR][curC] == 'c') {
+                return current;
+            }
+
+            if (visited[curR][curC]) {
+                continue;
+            }
+
+            visited[curR][curC] = true;
+
+            List<int[]> nextMoves = possibleMoves(maze, current);
+            queue.addAll(nextMoves);
+        }
+
+        throw new HungryRatException();
+    }
+
+    public static List<int[]> possibleMoves(char[][] maze, int[] currentLoc) {
+        List<int[]> moves = new ArrayList<>();
+        int[][] steps = {
+            {1, 0},
+            {-1, 0},
+            {0, 1},
+            {0, -1}
+        };
+
+        int curR = currentLoc[0];
+        int curC = currentLoc[1];
+
+        for (int[] step : steps) {
+            int newR = curR + step[0];
+            int newC = curC + step[1];
+
+            if (newR >= 0 && newR < maze.length && newC >= 0 && newC < maze[0].length && maze[newR][newC] != 'w') {
+                moves.add(new int[]{newR, newC});
+            }
+        }
+
+        return moves;
+    }
+
+    public static int[] findRat(char[][] maze) throws CrowdedMazeException, EscapedRatException {
+        int ratCount = 0;
+        int[] ratLocation = null;
+
+        for (int r = 0; r < maze.length; r++) {
+            for (int c = 0; c < maze[0].length; c++) {
+                if(maze[r][c] == 'R') {
+                    ratLocation = new int[]{r, c};
+                    ratCount++;
+                }
+            }
+        }
+
+        if (ratCount > 1) throw new CrowdedMazeException();
+        if (ratCount == 0) throw new EscapedRatException();
+
+        return ratLocation;
     }
 }

src/SearchTest.java

@@ -1,3 +1,58 @@
-public class SearchTest {
-
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class SearchTest {
+
+    @Test
+    void testNearestCheese_NormalCase() throws Exception {
+        char[][] maze = {
+            {'o', 'o', 'o', 'o', 'c', 'w', 'c', 'o'},
+            {'w', 'o', 'o', 'w', 'w', 'c', 'w', 'o'},
+            {'o', 'o', 'o', 'o', 'R', 'w', 'o', 'o'},
+            {'o', 'o', 'w', 'w', 'w', 'o', 'o', 'o'},
+            {'o', 'o', 'o', 'o', 'c', 'o', 'o', 'o'},
+        };
+
+        int[] result = Search.nearestCheese(maze);
+        assertArrayEquals(new int[]{0, 4}, result);
+    }
+
+    @Test
+    void testNearestCheese_NoRat_ThrowsEscapedRatException() {
+        char[][] maze = {
+            {'o', 'o', 'c'},
+            {'o', 'w', 'o'},
+            {'c', 'o', 'o'}
+        };
+
+        assertThrows(EscapedRatException.class, () -> {
+            Search.nearestCheese(maze);
+        });
+    }
+
+    @Test
+    void testNearestCheese_MultipleRats_ThrowsCrowdedMazeException() {
+        char[][] maze = {
+            {'R', 'o', 'R'},
+            {'o', 'w', 'c'},
+            {'c', 'o', 'o'}
+        };
+
+        assertThrows(CrowdedMazeException.class, () -> {
+            Search.nearestCheese(maze);
+        });
+    }
+
+    @Test
+    void testNearestCheese_NoReachableCheese_ThrowsHungryRatException() {
+        char[][] maze = {
+            {'R', 'w', 'c'},
+            {'w', 'w', 'w'},
+            {'c', 'w', 'c'}
+        };
+
+        assertThrows(HungryRatException.class, () -> {
+            Search.nearestCheese(maze);
+        });
+    }
 }