leetcode 289. Game of Life | 289. 生命游戏（Java）

女爷i 2022-10-12 14:59 139阅读 0赞

## 题目 ##

[https://leetcode.com/problems/game-of-life/][https_leetcode.com_problems_game-of-life]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 题解 ##

首先，遍历整个棋盘，如果是 1，就将上下左右的 count 值加 1。

然后，没有任何技巧，就是根据 count 值，拆 if-else。

如果要原地操作的话，可以使用位运算，**一个 int 有 32 bit，输入数据只用了一个 bit，所以我们可以利用其他空闲的bit位进行“原地修改”**。本文不再详述，可参考：[https://leetcode-cn.com/problems/game-of-life/solution/c-wei-yun-suan-yuan-di-cao-zuo-ji-bai-shuang-bai-b/][https_leetcode-cn.com_problems_game-of-life_solution_c-wei-yun-suan-yuan-di-cao-zuo-ji-bai-shuang-bai-b]

class Solution { 
        public void gameOfLife(int[][] board) { 
            int M = board.length;
            int N = board[0].length;
            int[][] cnt = new int[M][N];
            for (int i = 0; i < M; i++) { 
                for (int j = 0; j < N; j++) { 
                    if (board[i][j] == 1) { 
                        if (i > 0) cnt[i - 1][j]++;
                        if (j > 0) cnt[i][j - 1]++;
                        if (i > 0 && j > 0) cnt[i - 1][j - 1]++;
                        if (i < M - 1) cnt[i + 1][j]++;
                        if (j < N - 1) cnt[i][j + 1]++;
                        if (i < M - 1 && j < N - 1) cnt[i + 1][j + 1]++;
                        if (i < M - 1 && j > 0) cnt[i + 1][j - 1]++;
                        if (i > 0 && j < N - 1) cnt[i - 1][j + 1]++;
                    }
                }
            }
    
            for (int i = 0; i < M; i++) { 
                for (int j = 0; j < N; j++) { 
                    if (board[i][j] == 1 && cnt[i][j] < 2 || cnt[i][j] > 3) board[i][j] = 0;
                    if (board[i][j] == 0 && cnt[i][j] == 3) board[i][j] = 1;
                }
            }
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]

[https_leetcode.com_problems_game-of-life]: https://leetcode.com/problems/game-of-life/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]: /images/20221005/b6545f0d2c614adf882c12d75911d910.png
[https_leetcode-cn.com_problems_game-of-life_solution_c-wei-yun-suan-yuan-di-cao-zuo-ji-bai-shuang-bai-b]: https://leetcode-cn.com/problems/game-of-life/solution/c-wei-yun-suan-yuan-di-cao-zuo-ji-bai-shuang-bai-b/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20221005/5b1f697864f24dfeb2f9028acb6b6cc9.png