生命游戏

// Java Stream解法（受限于Stream的使用场景，这里仅用作计数）：
// 题目思路：我们无法直接用Stream来遍历和更新二维数组，但可以用Stream来辅助计数活细胞。
 
public class GameOfLifeStream {
    public void gameOfLife(int[][] board) {
        int m = board.length, n = board[0].length;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                long liveNeighbors = countLiveNeighbors(board, i, j);
                if (board[i][j] == 1 && (liveNeighbors < 2 || liveNeighbors > 3)) {
                    board[i][j] = 2;
                }
                if (board[i][j] == 0 && liveNeighbors == 3) {
                    board[i][j] = -1;
                }
            }
        }
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (board[i][j] == 2) board[i][j] = 0;
                if (board[i][j] == -1) board[i][j] = 1;
            }
        }
    }
    private long countLiveNeighbors(int[][] board, int i, int j) {
        int[][] directions = {{-1, -1}, {-1, 0}, {-1, 1}, {0, -1}, {0, 1}, {1, -1}, {1, 0}, {1, 1}};
        return Arrays.stream(directions)
                .filter(dir -> {
                    int x = i + dir[0], y = j + dir[1];
                    return x >= 0 && x < board.length && y >= 0 && y < board[0].length && Math.abs(board[x][y]) == 1;
                })
                .count();
    }
}