[LeetCode] 289. Game of Life

(1) Add a new 2D array to hold the new state - O(n ^ 2) space
(2) Bit operation - in place

public class Solution {
    public void gameOfLife(int[][] board) {
        if (board == null || board.length == 0 || board[0].length == 0) {
            return;
        }
        int[][] newState = new int[board.length][board[0].length];
        for (int i = 0; i < board.length; i++) {
            for (int j = 0; j < board[0].length; j++) {
                board[i][j] = isLive(i, j, board);
            }
        }
        for (int i = 0; i < board.length; i++) {
            for (int j = 0; j < board[0].length; j++) {
                board[i][j] = board[i][j] >> 1;
            }
        }
    }
    
    private int isLive(int i, int j, int[][] board) {
        int liveNeighbor = 0;
        for (int m = i - 1; m < board.length && m <= i + 1; m++) {
            for (int n = j - 1; n < board[0].length && n <= j + 1; n++) {
                if (m < 0 || n < 0 || (m == i && n == j)) {
                    continue;
                }
                if ((board[m][n] & 0x0001) == 1) {
                    liveNeighbor++;
                }
            }
        }
        if (liveNeighbor <= 1 || liveNeighbor >= 4) {
            return board[i][j];
        } 
        if (liveNeighbor == 3) {
            return (board[i][j] | 2);
        }
        return (board[i][j] | (board[i][j] << 1));
    }
}