Leetcode 289 Solution

This article provides solution to leetcode question 289 (game-of-life)
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https://leetcode.com/problems/game-of-life

Solution

class Solution {
public:
    void gameOfLife(vector<vector<int>>& board) {
        int m = board.size();
        if (m == 0)
            return;
        int n = board[0].size();



        const int dx[8] = {-1, -1, -1, 0, 1, 1, 1, 0};
        const int dy[8] = {-1, 0, 1, 1, 1, 0, -1, -1};



        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                int cnt = 0;



                for (int k = 0; k < 8; k++)
                {
                    if (i + dy[k] < 0 || i + dy[k] >= m)
                        continue;



                    if (j + dx[k] < 0 || j + dx[k] >= n)
                        continue;



                    if (board[i + dy[k]][j + dx[k]] & 1)
                        cnt++;
                }



                if (((board[i][j] & 1) == 1) && cnt >= 2 && cnt <= 3)
                    board[i][j] |= 2;
                else if (((board[i][j] & 1) == 0) && cnt == 3)
                    board[i][j] |= 2;
            }
        }



        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                board[i][j] = board[i][j] >> 1;
            }
        }
    }
};