LeetCode_生命遊戲_Array_M

289. 生命遊戲

class Solution {
	public void gameOfLife(int[][] board) {
		List<IndexNum> modifyList = new ArrayList<>();    //存需要改變的座標
		int m = board.length, n = board[0].length;
		// 座標數組
		int[] dx = {-1, -1, -1, 0, 0 ,1, 1, 1};
		int[] dy = {-1, 0, 1, -1, 1, -1, 0, 1};
		for (int i = 0; i < m; i++) {
			for (int j = 0; j < n; j++) {
				int count = 0;
				for (int k = 0; k < 8; k++) {
					int x = i + dx[k];
					int y = j + dy[k];
					if (x < 0 || x >= m || y < 0 || y >= n) {
						continue;
					}
					if (board[x][y] == 1) {
						count++;
					}	
				}
				if (board[i][j] == 0 && count == 3) {	// 死細胞
					modifyList.add(new IndexNum(i, j));
				} else if (board[i][j] == 1 && (count < 2 || count > 3)) {	// 活細胞
					modifyList.add(new IndexNum(i, j));
				}
			}
		}
		for (IndexNum index : modifyList) {
			if (board[index.x][index.y] == 0) {
				board[index.x][index.y] = 1;
			} else {
				board[index.x][index.y] = 0;
			}
		}
	}

	class IndexNum {
		int x;
		int y;
		IndexNum(int x, int y) {
			this.x = x;
			this.y = y;
		}
	}
}

不用額外的內存空間：

class Solution {

    // 複合狀態： 從活的變成死的用-1表示、從死的變成活的用2表示

    public void gameOfLife(int[][] board) {
        if (board == null) {
            return;
        }
        int m = board.length, n = board[0].length;
        int[] dx = {-1, -1, -1, 0, 0, 1, 1, 1};
        int[] dy = {-1, 0, 1, -1, 1, -1, 0, 1};
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                int count = 0;
                for (int k = 0; k < 8; k++) {
                    int x = i + dx[k];
                    int y = j + dy[k];
                    if ((x >= 0 && x < m) && (y >= 0 && y < n) && (board[x][y] == 1 || board[x][y] == -1)) {
                        count++;
                    }
                }
                if (board[i][j] == 0 && count == 3) {
                    board[i][j] = 2;    //死的變活
                } else if (board[i][j] == 1 && (count < 2 || count > 3)) {
                    board[i][j] = -1;   //活的變死
                }
            }
        }
        for (int i = 0; i < m ; i++) {
            for (int j = 0; j < n; j++) {
                if (board[i][j] == -1) {
                    board[i][j] = 0;
                } else if (board[i][j] == 2) {
                    board[i][j] = 1;
                }
            }
        }
    }
}