diff --git a/src/Location.java b/src/Location.java new file mode 100644 index 0000000..77ef752 --- /dev/null +++ b/src/Location.java @@ -0,0 +1,3 @@ +public record Location(int row, int col) { + +} diff --git a/src/Search.java b/src/Search.java index cebb278..0561ba1 100644 --- a/src/Search.java +++ b/src/Search.java @@ -1,5 +1,25 @@ +import java.util.ArrayList; +import java.util.HashMap; +import java.util.HashSet; +import java.util.LinkedList; +import java.util.List; +import java.util.Queue; +import java.util.Set; +import java.util.Map; public class Search { - /** + public static void main(String[] args) { + // Location myLoc = new Location(5, 88); + + char[][] grid = { + {'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'} + }; + System.out.println(nearestCheese(grid)); + } + /** * 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 * cheeses that are tied for the same shortest distance to reach, return @@ -29,6 +49,80 @@ public class Search { * @throws HungryRatException if there is no reachable cheese */ public static int[] nearestCheese(char[][] maze) throws EscapedRatException, CrowdedMazeException, HungryRatException { - return null; + Location startLoc = findRat(maze); + Queue queue = new LinkedList<>(); + queue.add(startLoc); + Set visited = new HashSet<>(); + + Map prevs = new HashMap<>(); + while(!queue.isEmpty()) { + Location current = queue.poll(); + if (maze[current.row()][current.col()] == 'c') { + List path = new ArrayList<>(); + Location pointer = current; + while(pointer.equals(startLoc)) { + path.add(pointer); + pointer = prevs.get(pointer); + } + + path.add(startLoc); + + System.out.println(path.reversed()); + return new int[] {current.row(), current.row()}; + }; + + + for (Location neighbor : neighbors(maze, current)) { + if (visited.contains(neighbor)) continue; + visited.add(neighbor); + queue.add(neighbor); + prevs.put(neighbor, current); + }; + } + + throw new HungryRatException(); + } + + public static List neighbors(char[][] maze, Location currentLoc) { + List result = new ArrayList<>(); + + int[] [] moves = new int[][] { + { -1, 0 }, //up + { 1, 0 }, //down + { 0, -1 }, //left + { 0, 1 }, //right + + }; + + for(int[] move : moves) { + int newR = currentLoc.row() + move[0]; + int newC = currentLoc.col() + move[1]; + + if(newR >= 0 && newR < maze.length && newC >=0 && newC < maze[0].length && maze[newR][newC] != 'w'){ + result.add(new Location(newR, newC)); + } + } + return result; + } + + public static Location findRat(char[][] maze) throws EscapedRatException, CrowdedMazeException { + Location location = null; + for(int row = 0; row < maze.length; row++){ + for(int col=0; col < maze[row].length; col++){ + if(maze[row][col] == 'R'){ + if(location == null){ + location = new Location(row, col); + } else{ + throw new CrowdedMazeException(); + } + } + } + } + + if(location == null){ + throw new EscapedRatException(); + } + + return location; } } \ No newline at end of file