2018 - Check if Word Can Be Placed In Crossword.

Medium

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

• <code>1 <= m * n <= 2 * 10⁵</code>

• board[i][j] will be ' ', '#', or a lowercase English letter.

• 1 <= word.length <= max(m, n)

• word will contain only lowercase English letters.