289. Game of Life

class Solution {
    public void gameOfLife(int[][] board) {
        if (board == null || board.length == 0) return;
        
        int m = board.length, n = board[0].length;
        
        // Iterate through each cell
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                int liveNeighbors = countLiveNeighbors(board, i, j);
                
                // Rule 1 or Rule 3
                if (board[i][j] == 1 && (liveNeighbors < 2 || liveNeighbors > 3)) {
                    board[i][j] = -1; // -1 signifies the cell is currently live but will die
                }
                
                // Rule 4
                if (board[i][j] == 0 && liveNeighbors == 3) {
                    board[i][j] = 2; // 2 signifies the cell is currently dead but will live
                }
            }
        }
        
        // Update the board to the next state
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (board[i][j] > 0) {
                    board[i][j] = 1;
                } else {
                    board[i][j] = 0;
                }
            }
        }
    }
    
    private int countLiveNeighbors(int[][] board, int row, int col) {
        int m = board.length, n = board[0].length;
        int count = 0;
        
        // Iterate over all 8 neighbors
        for (int i = -1; i <= 1; i++) {
            for (int j = -1; j <= 1; j++) {
                if (i == 0 && j == 0) continue; // Skip the cell itself
                
                int r = row + i, c = col + j;
                if (r >= 0 && r < m && c >= 0 && c < n && Math.abs(board[r][c]) == 1) {
                    count++;
                }
            }
        }
        
        return count;
    }

}