You are given an `m x n` matrix `board`, representing the current state of a crossword puzzle. The crossword contains lowercase English letters (from solved words), `' '` to represent any empty cells, and `'#'` to represent any blocked cells.

A word can be placed horizontally (left to right or right to left) or vertically (top to bottom or bottom to top) in the board if:

- It does not occupy a cell containing the character `'#'`.
- The cell each letter is placed in must either be `' '` (empty) or match the letter already on the `board`.
- There must not be any empty cells `' '` or other lowercase letters directly left or right of the word if the word was placed horizontally.
- There must not be any empty cells `' '` or other lowercase letters directly above or below the word if the word was placed vertically.

Given a string `word`, return `true` if `word` can be placed in `board`, or `false` otherwise.

Example 1:

    Input: board = [["#", " ", "#"], [" ", " ", "#"], ["#", "c", " "]], word = "abc"
    Output: true
    Explanation: The word "abc" can be placed as shown above (top to bottom).

Example 2:

    Input: board = [[" ", "#", "a"], [" ", "#", "c"], [" ", "#", "a"]], word = "ac"
    Output: false
    Explanation: It is impossible to place the word because there will always be a space/letter above or below it.

Example 3:

    Input: board = [["#", " ", "#"], [" ", " ", "#"], ["#", " ", "c"]], word = "ca"
    Output: true
    Explanation: The word "ca" can be placed as shown above (right to left).

Constraints:

- `m == board.length`
- `n == board[i].length`
- `1 <= m * n <= 2 * 105`
- `board[i][j]` will be `' '`, `'#'`, or a lowercase English letter.
- `1 <= word.length <= max(m, n)`
- `word` will contain only lowercase English letters.