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This approach creates a copy of the original board. It calculates the new state for each cell using the current state from the original board while updating the new state in the copy. Once all cells have been processed, it updates the original board with the calculated states from the copy.
Time Complexity: O(m * n), where m is the number of rows and n is the number of columns, because each cell is visited once.
Space Complexity: O(m * n), due to the additional copy of the board.
1var gameOfLife = function(board) {
2 const m = board.length, n = board[0].length;
3 const copy = board.map(arr => arr.slice());
4
5 const directions = [[-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]];
6
7 for (let i = 0; i < m; i++) {
8 for (let j = 0; j < n; j++) {
9 let liveNeighbors = 0;
10 for (const [di, dj] of directions) {
11 const ni = i + di, nj = j + dj;
12 if (ni >= 0 && ni < m && nj >= 0 && nj < n && copy[ni][nj] === 1) {
13 liveNeighbors++;
14 }
15 }
16
17 if (copy[i][j] === 1 && (liveNeighbors < 2 || liveNeighbors > 3)) {
18 board[i][j] = 0;
19 } else if (copy[i][j] === 0 && liveNeighbors === 3) {
20 board[i][j] = 1;
21 }
22 }
23 }
24};
25The JavaScript implementation uses the map function to create a copy of the board. It then iteratively checks each cell's neighbors and counts the live ones by iterating through all possible neighboring positions. As it applies the update rules, it simultaneously updates the state of each cell directly in the original board.
This approach uses in-place updates by leveraging different state values. We introduce temporary states: 2 represents a cell that was originally live (1) but will be dead in the next state, and -1 represents a cell that was dead (0) but will be live in the next state. At the end, these temporary states are converted to the final states.
Time Complexity: O(m * n), where m is the number of rows and n is the number of columns.
Space Complexity: O(1), as no additional space is used beyond input storage.
1
The C solution uses the board itself to track changes by representing transitional states so the board can be accurately updated in one iteration by determining the final state in a second pass.