1 class Solution {
 2 public:
 3     void gameOfLife(vector<vector<int>>& board) {
 4         int m = board.size();
 5         if (!m)return;
 6         int n = board[0].size();
 7         if (!n)return;
 8         int live_cnt;
 9         for (int i = 0; i < m; ++i) {
10             live_cnt = 0;
11             for (int j = 0; j < n; ++j) {
12                 live_cnt = getLive(i, j, board);
13                 if (board[i][j] == 0 && live_cnt == 3)board[i][j] = 3;
14                 else if (board[i][j] == 1) {
15                     --live_cnt;//包含自身
16                     if (live_cnt < 2 || live_cnt>3)
17                         board[i][j] = 2;
18                 }
19             }
20         }
21         for (int i = 0; i < m; ++i) {
22             for (int j = 0; j < n; ++j) {
23                 if (board[i][j] == 2)
24                     board[i][j] = 0;
25                 else if (board[i][j] == 3)
26                     board[i][j] = 1;
27             }
28         }
29     }
30 private:
31     int getLive(int row, int col, vector<vector<int>> &board) {
32         int live_cnt = 0;
33         int m = board.size(), n = board[row].size();
34         for (int i = max(0, row - 1); i < min(m, row + 2); ++i) {
35             for (int j = max(0, col - 1); j < min(n, col + 2); ++j) {
36                 if (board[i][j] == 1 || board[i][j] == 2)
37                     ++live_cnt;
38             }
39         }
40         return live_cnt;
41     }
42 };