/**
knakul853
**/
class Solution {
public:
    void gameOfLife(vector<vector<int>>& board) {

        if(board.empty()) return ;

        int n = (int)board.size();
        int m = (int)board[0].size();

        for(int i=0; i<n; i++)   // [2nd bit 1st bit] <- after preocess remove the first bit( >>=1 );
        {
            for(int j=0; j<m; j++)
            {
                int lives = Lives(board, i, j);
                if(board[i][j] == 1 && lives >=2 && lives <= 3)
                {
                    board[i][j] = 3;   //  it will not change the current state.eg 01->11 only next state changed
                }

                else if( board[i][j] == 0 && lives == 3)
                {
                    board[i][j] = 2;
                }
            }
        }

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

    }

    private :
    int Lives(vector<vector<int>>&board, int i, int j )
    {
        int n = (int)board.size();
        int m = (int)board[0].size();

        int lives = 0;
        for(int k=max(0, i-1); k<=min(n-1, i+1); k++ )
        {
            for(int l=max(0, j-1); l<=min(m-1, j+1); l++ )
            {
                lives+=board[k][l]&1;
            }
        }

        lives -= board[i][j]&1;

        return lives;
    }
};