In-class bfs

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.
@@ -27,8 +32,124 @@ public class Search {
      * @throws EscapedRatException if there is no rat in the maze
      * @throws CrowdedMazeException if there is more than one rat in the maze
      * @throws HungryRatException if there is no reachable cheese
+     * 
+     * 
+     * First Step: Find the location of the rat by looping through the entire array (Throw exceptions if more than one or zero rats)
+     * 
+     * Second Step: Find the directions that a rat can go: (Filters walls, )
+     * 
+     * Third Step: Use breadth first search to find the CLOSEST cheese to the rat
      */
+
     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 = []
+        Queue<int[]> queue = new LinkedList<>();
+        //  queue.add(start)
+        queue.add(start);
+
+        //  while queue isn't empty 
+        while(!queue.isEmpty()) {
+
+            //  current = queue.pop
+            int[] current = queue.poll();
+            int curRow = current[0];
+            int curCol = current[1];
+
+            //  if visited: continue
+            if(visited[curRow][curCol]) continue;
+
+            //  mark visited 
+            visited[curRow][curCol] = true;
+
+
+            //  if current is cheese: return current 
+            if(maze[curRow][curCol] == 'c')
+            {
+                return current;
+            }
+
+            //  add neighbors to the queue
+            queue.addAll(getNeighbors(maze, current));
+        }
+
+        //  throw hungry
+        throw new HungryRatException();
+    }
+
+    //Getting the possible places the rat can go 
+    public static List<int[]> getNeighbors(char[][] maze, int[] current)
+    {
+        int curRow = current[0];
+        int curCol = current[1];
+
+        //UP (Subtract Row and the Column stays the same) [-1,0]
+
+        //DOWN (Add one to the row and the Column stays the same) [1,0]
+
+        //LEFT (Row stays the same and Column gets subtracted by one) [0,-1]
+
+        //RIGHT (Row stays the same and Column gets added by one) [0,1]
+
+        int[][] directions = {
+            {-1,0}, //UP
+            {1,0},  //DOWN
+            {0,-1}, //LEFT
+            {0,1},  //RIGHT
+
+        };
+
+        List<int[]> possibleMoves = new ArrayList<>();
+
+        for(int [] direction : directions)  //looping through the directions
+        {
+            int changeRow = direction[0];
+            int changeCol = direction[1];
+
+            int newRow = curRow + changeRow;
+            int newCol = curCol + changeCol;
+
+            if(newRow >= 0 && newRow < maze.length && 
+            newCol >= 0 && newCol < maze[newRow].length &&
+            maze[newRow][newCol] != 'w')
+            {
+                //valid move
+                int[] validMove = {newRow, newCol};
+                possibleMoves.add(validMove);
+            }
+        }
+        return possibleMoves;
+    }
+
+    //**Step 1**/
+    public static int[] ratLocation(char[][] maze) throws EscapedRatException, CrowdedMazeException {
+        int[] location = null;
+
+        //searching the maze...
+        for(int row = 0; row < maze.length; row++)
+        {
+            for(int col = 0; col < maze[0].length; col++)
+            {
+                if(maze[row][col] == 'R')
+                {
+                    if(location != null) {
+                        throw new CrowdedMazeException();   //if there's more than one rat found throw exception
+                    }
+
+                    location = new int[] {row, col};    //setting the location of the rat when it's found 
+                }
+            }
+        }
+
+        if(location == null)    //if the location is still null after going through the maze, throw exceptions
+        {
+            //Rat not found
+            throw new EscapedRatException();
+        }
+
+        return location;
     }
+
 }