289 生命游戏

https://leetcode.cn/leetbook/read/top-interview-questions-hard/xwk53e/

cost: 31m39s

class Solution {
public:
    void gameOfLife(vector<vector<int>>& board) {
        enum State {
            DeadDead = 0b1000,
            DeadAlive = 0b1100,
            AliveDead = 0b1001,
            AliveAlive = 0b1101,
        };
        for (int i = 0; i < board.size(); i++) {
            for (int j = 0; j < board[0].size(); j++) {
                auto [deadCnt, aliveCnt] = this->countDeadAndAlive(board, i, j);
                if (board[i][j] == 1) {
                    if (aliveCnt < 2) {
                        board[i][j] |= 0b1000;
                    } else if (aliveCnt == 2 || aliveCnt == 3) {
                        board[i][j] |= 0b1100;
                    } else if (aliveCnt > 3) {
                        board[i][j] |= 0b1000;
                    }
                } else {
                    if (aliveCnt == 3) {
                        board[i][j] |= 0b1100;
                    }
                }
            }
        }

        for (int i = 0; i < board.size(); i++) {
            for (int j = 0; j < board[0].size(); j++) {
                board[i][j] = (board[i][j] >> 2) & 0b01;
            }
        }
    }

private:
    std::tuple<int, int> countDeadAndAlive(vector<vector<int>>& board, int i,
                                           int j) {
        int deadCnt = 0;
        int aliveCnt = 0;
        for (int k = std::max(0, i - 1);
             k <= std::min(i + 1, static_cast<int>(board.size() - 1)); k++) {
            for (int n = std::max(0, j - 1);
                 n <= std::min(j + 1, static_cast<int>(board[0].size() - 1));
                 n++) {
                if (k == i && n == j) {
                    continue;
                }
                int tmp = board[k][n] & 0b11;
                if (tmp == 0) {
                    deadCnt++;
                } else if (tmp == 1) {
                    aliveCnt++;
                }
            }
        }
        return {deadCnt, aliveCnt};
    }
};