Implemented Search methods in a breadth-first-search

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 +34,87 @@ public class Search {
      * @throws HungryRatException if there is no reachable cheese
      */
     public static int[] nearestCheese(char[][] maze) throws EscapedRatException, CrowdedMazeException, HungryRatException {
-        return null;
+
+        // find starting location of rat
+        int[] start = findTheRat(maze);
+
+        // THIS IS NEW STUFF HERE >>>
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(start);
+
+        // boolean record, all false by default
+        boolean[][] visited = new boolean[maze.length][maze[0].length];
+
+        while (!queue.isEmpty()) {
+            int[] current = queue.poll();
+            int curR = current[0];
+            int curC = current[0];
+
+            // if the cheese is found, immediately return cheese
+            if (maze[curR][curC] == 'c') {
+                return current;
+            }
+
+            // if this spot has been visited, exit
+            if (visited[curR][curC]) {
+                continue;
+            }
+
+            // mark visited record to avoid visiting the same spot twice
+            visited[curR][curC] = true;
+
+            List<int[]> nextMoves = possibleMoves(maze, current);
+            // add all next moves to the end of the queue
+            queue.addAll(nextMoves);
+        }
+
+        throw new HungryRatException();
+    }
+
+    // find rat
+    public static int[] findTheRat(char[][] maze) throws CrowdedMazeException, EscapedRatException {
+        // keep track of two things: the location of the rat, and how many rats we've found
+
+        int ratCount = 0;
+        int[] ratLocation = null;
+
+        for (int row = 0; row < maze.length; row++) {
+            for (int col = 0; col < maze[0].length; col++) {
+                if (maze[row][col] == 'R') {
+                    ratLocation = new int[]{row, col};
+                    ratCount++;
+                }
+            }
+        }
+
+        if (ratCount > 1) throw new CrowdedMazeException();
+        if (ratCount == 0) throw new EscapedRatException();
+
+        return ratLocation;
+    }
+
+    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[0];
+
+            if (newR >= 0 && newR < maze.length && newC >= 0 && newC < maze[0].length && maze[newR][newC] != 'w') {
+                moves.add(new int[]{newR, newC});
+            }
+        }
+
+        return moves;
+
     }
 }