public void gameOfLife(int[][] board) {

if (board == null || board.length == 0 || board[0].length == 0) return;

int n = board.length;

int m = board[0].length;

int[][] newBoard = new int[n][m];

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

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

if (board[i][j] == 0) {

newBoard[i][j] = countLive(board, i, j) == 3 ? 1 : 0;

} else {

int lives = countLive(board, i, j);

newBoard[i][j] = (lives == 2 || lives == 3) ? 1 : 0;

}

}

}

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

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

board[i][j] = newBoard[i][j];

}

}

}

private int countLive(int[][] board, int x, int y) {

int n = board.length;

int m = board[0].length;

int res = 0;

for (int i=x-1; i<=x+1; i++) {

if (i < 0 || i >= n) continue;

for (int j=y-1; j<=y+1; j++) {

if (j < 0 || j >= m || (i == x && j == y)) continue;

if (board[i][j] == 1) res++;

}

}

return res;

}

/**

public void gameOfLife2(int[][] board) {

if (board == null || board.length == 0) return;

int m = board.length, n = board[0].length;

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

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

int lives = liveNeighbors(board, m, n, i, j);

// In the beginning, every 2nd bit is 0;

// So we only need to care about when will the 2nd bit become 1.

if (board[i][j] == 1 && lives >= 2 && lives <= 3) {

board[i][j] = 3; // Make the 2nd bit 1: 01 ---> 11

}

if (board[i][j] == 0 && lives == 3) {

board[i][j] = 2; // Make the 2nd bit 1: 00 ---> 10

}

}

}

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

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

board[i][j] >>= 1; // Get the 2nd state.

}

}

}

public int liveNeighbors(int[][] board, int m, int n, int i, int j) {

int lives = 0;

for (int x = Math.max(i - 1, 0); x <= Math.min(i + 1, m - 1); x++) {

for (int y = Math.max(j - 1, 0); y <= Math.min(j + 1, n - 1); y++) {

lives += board[x][y] & 1;

}

}

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

return lives;

}

public void gameOfLife3(int[][] board) {

int M = board.length;

int N = board[0].length;

for (int i=0; i<M; i++) {

for (int j=0; j<N; j++) {

update(board, i, j, M, N);

}

}

for (int i=0; i<M; i++) {

for (int j=0; j<N; j++) {

refresh(board, i, j);

}

}

}

private void update(int[][] board, int i, int j, int M, int N) {

int lives = 0;

for (int x=i-1; x<=i+1; x++) {

if (x < 0 || x >= M) continue;

for (int y=j-1; y<=j+1; y++) {

if (y < 0 || y >= N || (x == i && y == j)) continue;

if ((board[x][y] & 1) == 1) lives++;

}

}

boolean wasLive = (board[i][j] & 1) == 1;

if (wasLive) {

if (lives == 2 || lives == 3) {

board[i][j] |= 1 << 1;

}

} else {

if (lives == 3) {

board[i][j] |= 1 << 1;

}

}

}

private void refresh(int[][] board, int i, int j) {

board[i][j] = board[i][j] >> 1;

}