Game of Life.java

class Solution {
    public void gameOfLife(int[][] board) {
        
        if(board==null || board.length==0||board[0].length==0)
        return;
 
        int m=board.length;
        int n=board[0].length;
 
        int[] x = {-1, -1, 0, 1, 1, 1, 0, -1};
        int[] y = {0, 1, 1, 1, 0, -1, -1, -1};
 
        for(int i=0; i<m; i++){
            for(int j=0; j<n; j++){
                int count=0;
                for(int k=0; k<8; k++){
                    int nx=i+x[k];
                    int ny=j+y[k];
                    if(nx>=0&&nx<m&&ny>=0&&ny<n&&(board[nx][ny]&1)==1){
                        count++;
                    }
                }
                //<2 die
            if(count<2){
                board[i][j] &= 1;
            }
 
            //same state
            if(count==2||count==3){
                board[i][j] |=  board[i][j]<<1;
            }
 
            //go live
            if(count==3){
                board[i][j] |=2;
            }
 
            //>3 die
            if(count>3){
                board[i][j] &=1;
            }
            }
        }
 
        for(int i=0; i<m; i++){
            for(int j=0; j<n; j++){
                board[i][j] = board[i][j]>>1;
 
            }
        }
    }        
}