Boggle solver implementation

问题

I am struggling to implement a solution to finding all the words in a random 5x5 board of letters. Currently it is returning a few words but not nearly the full list. I am pretty sure that my problem exists within the findWords method with my for loops, but I can't figure out what to make the if statement to continue traversing in all 8 directions.

import java.io.File;
import java.util.*;
public class RandomWordGame {

    private static char[][] board = new char[5][5];
    private static Random r = new Random();
    private static ArrayList<String> dictionary = new ArrayList<String>();

    private static char[][] createBoard()
    {
        for (int i=0; i<board.length; i++)
        {
            for (int j=0; j<board.length; j++)
            {
                board[i][j] = (char) (r.nextInt(26) + 'a');
                System.out.print(board[i][j]);
            }
            System.out.println("");
        }
        System.out.println();
        return board;
    }
    public static ArrayList<String> solver(char[][] board)
    {
        if(board == null)
            System.out.println("Board cannot be empty");
        ArrayList<String> words = new ArrayList<String>();
        for(int i=0; i<board.length; i++)
        {
            for(int j=0; j<board[0].length; j++)
            {
                findWords(i, j, board[i][j] + "");
            }
        }
        return words;
    }
    public static void findWords(int i, int j, String currWord)
    {
        try
        {
            Scanner inputStream = new Scanner(new File("./dictionary.txt"));
            while(inputStream.hasNext())
            {
                dictionary.add(inputStream.nextLine());
            }
            inputStream.close();
        }catch(Exception e){
            e.printStackTrace();
        }

        for(i=0; i>=0 && i<board.length; i++)
        {
            for(j=0; j>=0; j++)
            {
                currWord += board[i][j];
                if(currWord.length()>5)
                    return;
                if(dictionary.contains(currWord))
                    System.out.println(currWord);
            }
        }
    }   
    public static void main(String[] args)
    {
        board = createBoard();
        ArrayList<String> validWords = RandomWordGame.solver(board);
        for(String word : validWords)
            System.out.println(word);
    }
}

回答1:

There are a few things funny with this code. For one, you are always returning an empty ArrayList from your solver method, but that isn't what's killing you because you are printing each result from findWords.

The problem is that the findWords method just continuously adds letters starting from the top left of the puzzle.

//i=0 and j=0 means it will always start at the top left tile
for(i=0; i>=0 && i<board.length; i++)
{
    for(j=0; j>=0; j++)
    {
        //currWord is never reset, so it just keeps getting longer
        currWord += board[i][j];
        if(currWord.length()>5)
            return;
        if(dictionary.contains(currWord))
            System.out.println(currWord);
    }
}

Right now you are only finding words that start with your chosen tile, and the rest of the letters are picked in the same order they were added to the puzzle starting from the top left.

I would recommend spending some quality time with a pencil and paper, and gaining an intimate understanding of the relationship between two dimensional array indexes and their position in a grid.

回答2:

Java implementation using DFS approach

    import java.util.Arrays;

    public class WordBoggle {

    static int[] dirx = { -1, 0, 0, 1 };
    static int[] diry = { 0, -1, 1, 0 };

    public static void main(String[] args) {
        char[][] board = { { 'A', 'B', 'C', 'E' }, { 'S', 'F', 'C', 'S' }, { 'A', 'D', 'E', 'E' } };

        String word = "ABFSADEESCCEA";
        System.out.println(exist(board, word));
    }

    static boolean exist(char[][] board, String word) {
        if (board == null || board.length == 0 || word == null || word.isEmpty())
            return false;
        boolean[][] visited = new boolean[board.length][board[0].length];
        for (int i = 0; i < board.length; i++) {
            resetVisited(visited);
            for (int j = 0; j < board[0].length; j++) {
                if (board[i][j] == word.charAt(i)) {
                    return DFS(board, word, i, j, 1, visited);
                }
            }
        }
        return false;
    }

    static void resetVisited(boolean[][] visited) {
        for (int l = 0; l < visited.length; l++) {
            Arrays.fill(visited[l], false);
        }
    }

    static boolean DFS(char[][] board, String word, int i, int j, int k, boolean[][] visited) {
        visited[i][j] = true;
        if (k >= word.length())
            return true;
        for (int z = 0; z < 4; z++) {
            if (isValid(board, i + dirx[z], j + diry[z], visited)) {
                if (word.charAt(k) == board[i + dirx[z]][j + diry[z]]) {

                    return DFS(board, word, i + dirx[z], j + diry[z], k + 1, visited);
                }

            }
        }
        return false;
    }

    static boolean isValid(char[][] board, int i, int j, boolean[][] visited) {
        return (i >= 0 && i < board.length && j >= 0 && j < board[0].length && !visited[i][j]);
    }
}

来源：https://stackoverflow.com/questions/40558761/boggle-solver-implementation