import java.util.*;

/**
 * @author Wang Guolong
 * @version 1.0
 * @date 2020/7/31 5:50 下午
 */
public class GenerateWordBoard {

 private static char[][] board;

 public static void main(String[] args) {
 GenerateWordBoard g = new GenerateWordBoard();
 g.generateCharBoard("vocabulary", 5, 5);
 }

 private void generateCharBoard(String word, int m, int n) {
 // 單詞為空 直接返回
 if (word.isEmpty()) {
  return;
 }
 // 單詞長(zhǎng)度大于棋盤(pán) 鋪不下 直接返回
 if (word.length() > m * n) {
  return;
 }
 // 初始化棋盤(pán) 全為*
 initBoard(m, n);

 char[] wordChar = word.toCharArray();
 // 隨機(jī)選取一個(gè)位置開(kāi)始
 Random random = new Random();
 int randomX = random.nextInt(m);
 int randomY = random.nextInt(n);
 // 開(kāi)始從隨機(jī)位置dfs鋪單詞 從index 0 開(kāi)始
 boolean result = generateDfs(board, wordChar, randomX, randomY, 0);
 // 如果沒(méi)有找到路線 那么從四個(gè)角開(kāi)始 必能找到一條路
 if (!result) {
  List<int[]> starts = Arrays.asList(new int[]{0, 0}, new int[]{0, n - 1}, new int[]{m - 1, 0},
   new int[]{m - 1, n - 1});
  // 隨機(jī)四個(gè)角的一個(gè)
  Collections.shuffle(starts);
  // 初始化棋盤(pán)
  initBoard(m, n);
  // dfs鋪單詞
  generateDfs(board, wordChar, starts.get(0)[0], starts.get(0)[1], 0);
 }
 // 查看結(jié)果
 for (int i = 0; i < board.length; i++) {
  for (int j = 0; j < board[0].length; j++) {
  System.out.print(board[i][j] + " ");
  }
  System.out.println();
 }
 }

 private void initBoard(int m, int n) {
 // 初始化
 board = new char[m][n];
 for (int i = 0; i < board.length; i++) {
  for (int j = 0; j < board[0].length; j++) {
  board[i][j] = '*';
  }
 }
 }

 /**
 * 返回true則為找到一條路 返回false為死路
 */
 private boolean generateDfs(char[][] board, char[] wordChar, int i, int j, int index) {
 // 碰到邊 或者碰到已經(jīng)走過(guò)的位置 不能走了 死路
 if (i >= board.length || i < 0 || j >= board[0].length || j < 0 || board[i][j] == '/') {
  return false;
 }

 // 擺放一個(gè)字母
 board[i][j] = wordChar[index];

 //如果已經(jīng)達(dá)到單詞長(zhǎng)度則直接返回 找到一條路
 if (index == wordChar.length - 1) {
  return true;
 }

 // 記錄當(dāng)前矩陣元素
 char tmp = board[i][j];
 // 修改為/ 表示已經(jīng)訪問(wèn)過(guò)
 board[i][j] = '/';

 // 向上下左右四個(gè)方向開(kāi)啟遞歸
 // 查看能走幾個(gè)方向 隨機(jī)選擇一個(gè)
 List<int[]> directions = Arrays.asList(new int[]{-1, 0}, new int[]{1, 0}, new int[]{0, -1}, new int[]{0, 1});
 Collections.shuffle(directions);

 boolean res = false;
 for (int k = 0; k < directions.size(); k++) {
  int di = i + directions.get(k)[0], dj = j + directions.get(k)[1];
  boolean partialRes = generateDfs(board, wordChar, di, dj, index + 1);
  if (k == 0) {
  res = partialRes;
  } else {
  res = res || partialRes;
  }
  // 如果res為true 說(shuō)明找到一條路 就不再遍歷了 還原后返回true
  if (res) {
  // 還原矩陣元素
  board[i][j] = tmp;
  return true;
  }
 }
 // 還原矩陣元素
 board[i][j] = '*';
 return false;
 }
}