pub fn exist(board: Vec<Vec<char>>, word: String) -> bool {

let word = word.as_bytes();

let mut board = board;

for i in 0..board.len() {

for j in 0..board[0].len() {

if board[i][j] as u8 == word[0] {

let x = board[i][j];

board[i][j] = '0';

if Self::scan(&mut board[..], &word[1..], (i, j)) {

return true;

}

board[i][j] = x;

}

}

}

false

}

fn scan(board: &mut [Vec<char>], word: &[u8], index: (usize, usize)) -> bool {

if word.len() == 0 {

return true;

}

if index.0 > 0 {

let x = board[index.0 - 1][index.1];

board[index.0 - 1][index.1] = '0';

if x != '0'

&& x as u8 == word[0]

&& Self::scan(board, &word[1..], (index.0 - 1, index.1))

{

return true;

}

board[index.0 - 1][index.1] = x;

}

if index.0 < board.len() - 1 {

let x = board[index.0 + 1][index.1];

board[index.0 + 1][index.1] = '0';

if x != '0'

&& x as u8 == word[0]

&& Self::scan(board, &word[1..], (index.0 + 1, index.1))

{

return true;

}

board[index.0 + 1][index.1] = x;

}

if index.1 > 0 {

let x = board[index.0][index.1 - 1];

board[index.0][index.1 - 1] = '0';

if x != '0'

&& x as u8 == word[0]

&& Self::scan(board, &word[1..], (index.0, index.1 - 1))

{

return true;

}

board[index.0][index.1 - 1] = x;

}

if index.1 < board[0].len() - 1 {

let x = board[index.0][index.1 + 1];

board[index.0][index.1 + 1] = '0';

if x != '0'

&& x as u8 == word[0]

&& Self::scan(board, &word[1..], (index.0, index.1 + 1))

{

return true;

}

board[index.0][index.1 + 1] = x;

}

false

}