if(i < 0 || i >= m || j < 0 || j >= n || board[i][j] != word.charAt(idx))
        return false;
    
    char temp = board[i][j];
    board[i][j] = '$';
    
    for(int[] dir : directions) {
        int i_ = i   dir[0];
        int j_ = j   dir[1];
        
        if(find(board, i_, j_, word, idx 1))
            return true;
    }
    
    board[i][j] = temp;
    return false;
}
public boolean exist(char[][] board, String word) {
    m = board.length;
    n = board[0].length;
    l = word.length();
    if(m*n < 1)
        return false;
    for(int i = 0; i<m; i  ) {
        for(int j = 0; j<n; j  ) {
            if(board[i][j] == word.charAt(0) && find(board, i, j, word, 0)) {
                return true;
            }
        }
    }
    
    return false;
}