题目：

题解：

class Solution {public boolean exist(char[][] board, String word) {char[] words = word.toCharArray();for(int i = 0; i < board.length; i++) {for(int j = 0; j < board[0].length; j++) {if (dfs(board, words, i, j, 0)) return true;}}return false;}boolean dfs(char[][] board, char[] word, int i, int j, int k) {if (i >= board.length || i < 0 || j >= board[0].length || j < 0 || board[i][j] != word[k]) return false;if (k == word.length - 1) return true;board[i][j] = '\0';boolean res = dfs(board, word, i + 1, j, k + 1) || dfs(board, word, i - 1, j, k + 1) || dfs(board, word, i, j + 1, k + 1) || dfs(board, word, i , j - 1, k + 1);board[i][j] = word[k];return res;}
}