leetcode/0289_game-of-life/python3/extra_space.py

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2022-04-13 00:07:19 +00:00
# Time: O(m*n)
# Space: O(m*n)
class Solution:
def gameOfLife(self, board: List[List[int]]) -> None:
"""
Do not return anything, modify board in-place instead.
"""
nrows, ncols = len(board), len(board[0])
board_copy = [[None] * ncols for _ in range(nrows)]
for i in range(nrows):
for j in range(ncols):
board_copy[i][j] = next_cell_state(board, i, j)
# Copy new board values
for i in range(nrows):
for j in range(ncols):
board[i][j] = board_copy[i][j]
def next_cell_state(board, i, j):
current = board[i][j]
total_alive = sum(get_cell_neighbours(board, i, j))
# Rule 4: Exact 3 neighbors will mean dead cell becomes alive
# Live cell remains live
if total_alive == 3:
return 1
# Rule 2: Live cell lives onto next generation
# Dead cell remains dead
elif total_alive == 2:
return current
# Rules 1 and 2: Under-population and over-population
return 0
# Return cell at (i, j) or 0 if it's out of bounds
def cell(board, i, j):
nrows, ncols = len(board), len(board[0])
return board[i][j] if 0 <= i < nrows and 0 <= j < ncols else 0
# Get surrounding 8 neighbours of cell at (i, j)
def get_cell_neighbours(board, i, j):
return (
cell(board, i - 1, j - 1), cell(board, i - 1, j), cell(board, i - 1, j + 1),
cell(board, i, j - 1), cell(board, i, j + 1),
cell(board, i + 1, j - 1), cell(board, i + 1, j), cell(board, i + 1, j + 1)
)