289. Game of Life | LeetCode | Top Interview 150 | Coding Questions

Problem Link

https://leetcode.com/problems/game-of-life/

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Detailed Step-by-Step Explanation

https://leetcode.com/problems/game-of-life/solutions/7473408/smartest-approach-beats-100-most-optimal-p3g3

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Solution

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

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

        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                int liveNeighbors = countLiveNeighbors(board, i, j);
                if (board[i][j] == 1) {
                    if (liveNeighbors < 2 || liveNeighbors > 3) {
                        board[i][j] = 2;
                    }
                } else {
                    if (liveNeighbors == 3) {
                        board[i][j] = 3;
                    }
                }
            }
        }

        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (board[i][j] == 2) board[i][j] = 0;
                else if (board[i][j] == 3) board[i][j] = 1;
            }
        }
    }

    private int countLiveNeighbors(int[][] board, int i, int j) {
        int count = 0;
        int n = board.length;
        int m = board[0].length;

        int[] dx = {-1, -1, -1, 0, 0, 1, 1, 1};
        int[] dy = {-1, 0, 1, -1, 1, -1, 0, 1};

        for (int d = 0; d < 8; d++) {
            int ni = i + dx[d];
            int nj = j + dy[d];

            if (ni >= 0 && ni < n && nj >= 0 && nj < m) {
                if (board[ni][nj] == 1 || board[ni][nj] == 2) {
                    count++;
                }
            }
        }
        return count;
    }
}