diff --git a/src/Search.java b/src/Search.java index cebb278..de5e6bb 100644 --- a/src/Search.java +++ b/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 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 nextMoves = possibleMoves(maze, current); + + queue.addAll(nextMoves); + } + + throw new HungryRatException(); + } + + public static List possibleMoves(char[][] maze, int[] currentLocation) { + List 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; } } \ No newline at end of file diff --git a/src/SearchTest.java b/src/SearchTest.java index 70b01de..8363664 100644 --- a/src/SearchTest.java +++ b/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); + }); + } +} \ No newline at end of file