BFS Livecode

src/Search.java

@@ -1,3 +1,8 @@
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
 public class Search {
      /**
      * Finds the location of the nearest reachable cheese from the rat's position.
@@ -29,6 +34,73 @@ public class Search {
      * @throws HungryRatException if there is no reachable cheese
      */
     public static int[] nearestCheese(char[][] maze) throws EscapedRatException, CrowdedMazeException, HungryRatException {
-        return null;
+        boolean[][] visited = new boolean[maze.length][maze[0].length];
+        int[] start = ratLocation(maze);
+
+        Queue<int[]> queue =  new LinkedList<>();
+        queue.add(start);
+
+        while(!queue.isEmpty()) {
+            int[] current = queue.poll();
+            int curR = current[0];
+            int curC = current[1];
+            if(visited[curR][curC]) continue;
+            visited[curR][curC] = true;
+            if(maze[curR][curC]== 'c') return current;
+            queue.addAll(getNeighbors(maze, current));
+        }
+
+        throw new HungryRatException();
     }
+
+
+    public static List<int[]> getNeighbors(char[][] maze, int[]current) {
+        int curR = current[0];
+        int curC = current[1];
+
+        int[][] directions = {
+            {-1, 0},// UP
+            {1, 0}, // DOWN
+            {0, -1}, // LEFT
+            {1, 0} // RIGHT
+        };
+        List<int[]> possibleMoves = new ArrayList<>();
+
+        for(int[] direction : directions) {
+            int changeR = direction[0];
+            int changeC = direction[1];
+            int newR = curR + changeR;
+            int newC = curC + changeC;
+
+            if(newR >= 0 && newR < maze.length && 
+                newC >= 0 &&  newC < maze[newR].length && 
+                maze[newR][newC] !='w') {
+
+                // valid move
+                int[] validMove = {newR, newC};
+                possibleMoves.add(validMove);
+            }
+        }
+
+        return possibleMoves;
+    }
+
+
+    public static int[] ratLocation(char[][] maze) throws EscapedRatException, CrowdedMazeException {
+        int[] location = null;
+
+        for(int r = 0; r < maze.length; r++){
+            for(int c = 0; c < maze[r].length; c++) {
+                if(maze[r][c] == 'R') {
+                    if(location !=null) throw new CrowdedMazeException();
+                    location = new int[]{r, c};
+                }
+            }
+        }
+
+        if(location == null) throw new EscapedRatException();
+
+        return location;
+    }
+
 }