bfs core code completed

src/Search.java

@@ -1,4 +1,10 @@
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
 public class Search {
+    // to find nearest or closest use BFS
      /**
      * Finds the location of the nearest reachable cheese from the rat's position.
      * Returns a 2-element int array: [row, col] of the closest 'c'. If there are multiple
@@ -29,6 +35,78 @@ 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 = ratLocation(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[] currentLocation) {
+        List<int[]> moves = new ArrayList<>();
+
+        int[][] steps = {
+            {-1, 0},
+            {1, 0},
+            {0, -1},
+            {0, 1}
+        };
+
+        int curR = currentLocation[0];
+        int curC = currentLocation[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[] ratLocation(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') {
+                    ratCount++;
+                    ratLocation = new int[]{r, c};
+                }
+            }
+        }
+        if(ratCount > 1) throw new CrowdedMazeException();
+        if(ratCount == 0) throw new EscapedRatException();
+        return ratLocation;
     }
 }

src/SearchTest.java

@@ -1,3 +1,64 @@
+import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.Test;
+
 public class SearchTest {
-
-}
+
+    @Test
+    public void testNearestCheese() 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
+    public void testThrowsCrowdedMazeException() {
+        char[][] maze = {
+            {'R','o','o','o','c','w','c','o'},
+            {'w','R','o','w','w','c','w','R'},
+            {'o','o','o','o','o','w','o','o'},
+            {'o','o','w','w','w','o','o','o'},
+            {'R','o','o','o','c','o','R','o'}
+        };
+
+        assertThrows(CrowdedMazeException.class, () -> {
+            Search.nearestCheese(maze);
+        });
+    }
+
+    @Test
+    public void testThrowsEscapedRatException() {
+        char[][] maze = {
+            {'o','o','o','o','c','w','c','o'},
+            {'w','o','o','w','w','c','w','o'},
+            {'o','o','o','o','o','w','o','o'},
+            {'w','o','w','w','w','o','o','o'},
+            {'w','w','o','o','c','o','o','o'}
+        };
+
+        assertThrows(EscapedRatException.class, () -> {
+            Search.nearestCheese(maze);
+        });
+    }
+
+    @Test
+    public void testThrowsHungryRatException() {
+        char[][] maze = {
+            {'w','w','w','w','c','w','c','w'},
+            {'w','w','w','c','w','c','w','w'},
+            {'w','w','w','w','R','w','w','w'},
+            {'w','w','w','c','w','c','w','w'},
+            {'w','w','w','w','c','w','w','w'}
+        };
+
+        assertThrows(HungryRatException.class, () -> {
+            Search.nearestCheese(maze);
+        });
+    }
+}