add py3 soln for game of life

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

@@ -0,0 +1,49 @@
+# 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)
+    )