79_word_search.java

class Solution {
    public boolean exist(char[][] board, String word) {
        boolean[][] visited = new boolean[board.length][board[0].length];
        boolean ans = false;
        for (int i = 0; i < board.length; i++) {
            for (int j = 0; j < board[0].length; j++) {
                ans = backtracking(board, visited, i, j, word, 0);
                if (ans == true) {
                    return true;
                }
            }
        }
        return false;
    }

    public boolean backtracking(char[][] board, boolean[][] visited, int i, int j, String word, int k) {
        if (board[i][j] != word.charAt(k)) {
            return false;
        }
        if (k == word.length() - 1) {
            return true;
        }
        boolean ans = false;
        int[][] directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
        visited[i][j] = true;
        for (int[] tmp: directions) {
            int newI = i + tmp[0];
            int newJ = j + tmp[1];
            if (newI >= 0 && newI < board.length && newJ >= 0 && newJ < board[0].length) {
                if (visited[newI][newJ] == false) {
                    ans = backtracking(board, visited, newI, newJ, word, k+1);
                    if (ans == true) {
                        break;
                    }
                }
            }
        }
        visited[i][j] = false;
        return ans;
    }
}

/**
 * This is my personal record of solving Leetcode Problems. 
 * If you have any questions, please discuss them in [Issues](https://github.com/mengxinayan/leetcode/issues).
 * Copyright (C) 2020-2022  mengxinayan
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */