Final matrix problem, this one a bit special to me. My first repo in Github is for a Game of Life program in C++. I created it in 2011 as a science fair project.

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Solution

This method uses constant space by usind integer division and modulo operations. We use this to update state in-place, then we traverse over the grid again to convert the values back to 0 or 1.

class Solution:
    def gameOfLife(self, board: List[List[int]]) -> None:
        """
        Do not return anything, modify board in-place instead.
        """
        neighbors = [(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, -1), (1, 0), (1, 1)]
        for i, row in enumerate(board):
            for j, cell in enumerate(row):
                neighborCount = 0
                for (nx, ny) in neighbors:
                    y, x = i + ny, j + nx
                    if (x >= 0 and y >= 0 and
                        x < len(board[0]) and y < len(board) and
                        board[y][x] % 2):
                        neighborCount += 1
                if cell % 2 and neighborCount < 2:
                    pass
                elif cell % 2 and neighborCount == 2 or neighborCount == 3:
                    board[i][j] += 2
                elif cell % 2 and neighborCount > 3:
                    pass
                elif not cell % 2 and neighborCount == 3:
                    board[i][j] += 2
        
        for i in range(len(board)):
            for j in range(len(board[0])):
                board[i][j] = board[i][j] // 2
``
(n) = m * n