Main79.java

package HOT100;

public class Main79 {
    public boolean exist(char[][] board, String word) {
        int n = board.length;
        int m = board[0].length;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if(board[i][j] == word.charAt(0)) {
                    if(dfs(board, word, i, j, 0)){
                        return true;
                    }
                }
            }
        }
        return false;
    }

    private boolean dfs(char[][] board, String word, int i, int j, int index) {
        if(index == word.length()) {
            return true;
        }
        if(i < 0 || j < 0 || i >= board.length || j >= board[0].length) {
            return false;
        }
        if(board[i][j] != word.charAt(index)) {
            return false;
        }
        char c = board[i][j];
        board[i][j] = '\0';
        boolean res = dfs(board, word, i + 1, j, index + 1) || dfs(board, word, i - 1, j, index + 1)
        || dfs(board, word, i, j + 1, index + 1) || dfs(board, word, i, j - 1, index + 1);
        board[i][j] = c;
        return res;
    }
}