A minesweeper field is a grid of strings where "*" marks a mine and "." an empty cell. Return a
new grid of integers: each mine becomes -1, and each empty cell becomes the number of mines
among its eight neighbours.
Examples
Input: field = [[".", "*"],
[".", "."]]
Output: [[1, -1],
[1, 1]]
Input: field = [["*", "*"],
["*", "*"]]
Output: [[-1, -1],
[-1, -1]]
Input: field = [["."]]
Output: [[0]]
Constraints
1 <= rows, cols <= 100
Goals
- Count 8-directional neighbours matching a value
- Produce an integer grid from a character grid