60. Game of Life

Topic :

matrix

Difficulty :

medium

Problem Link :

problem statement

According to Wikipedia's article: "The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970."

The board is made up of an m x n grid of cells, where each cell has an initial state: live (represented by a 1) or dead (represented by a 0). Each cell interacts with its eight neighbors (horizontal, vertical, diagonal) using the following four rules (taken from the above Wikipedia article):

Any live cell with fewer than two live neighbors dies as if caused by under-population.
Any live cell with two or three live neighbors lives on to the next generation.
Any live cell with more than three live neighbors dies, as if by over-population.
Any dead cell with exactly three live neighbors becomes a live cell, as if by reproduction.

The next state is created by applying the above rules simultaneously to every cell in the current state, where births and deaths occur simultaneously. Given the current state of the m x n grid board, return the next state.

Example 1:

Input: board = [[0,1,0],[0,0,1],[1,1,1],[0,0,0]]
Output: [[0,0,0],[1,0,1],[0,1,1],[0,1,0]]

Input: board = [[1,1],[1,0]]
Output: [[1,1],[1,1]]

Constraints:

m == board.length
n == board[i].length
1 <= m, n <= 25
board[i][j] is 0 or 1.

solution

import java.io.*;
import java.util.*;
class Game_of_Life
{
    public static void main (String args[])
    {
        int [][] board={{0,1,0},{0,0,1},{1,1,1},{0,0,0}};
        int rows=board.length;
        int cols=board[0].length;
        for(int i=0;i<rows;i++)
        { for (int j=0;j<cols;j++)
            {
                System.out.print(board[i][j]+" ");
            }
            System.out.println();
        }
        gameOfLife(board);
        System.out.println();
         for(int i=0;i<rows;i++)
        { for (int j=0;j<cols;j++)
            {
                System.out.print(board[i][j]+" ");
            }
            System.out.println();
        }
    }
    static void gameOfLife(int[][] board) {
          // 0 and stays 0 
         // 1 and stays 1
        // 0 and becomes alive then 2
       // 1 and becomes dead then 3
      // check count of 1 and 3 at 8 positions
        
      int n=board.length;
      int m=board[0].length;
        
      for(int i=0;i<n;i++)
      { for(int j=0;j<m;j++)
         {
           if(board[i][j]==1)
           {
             if(countOnes(board,i,j)<2 || countOnes(board,i,j)>3)
                 board[i][j]=3;
           }
          
          else
              
          {
              if(countOnes(board,i,j)==3)
                  board[i][j]=2;
          }
          
          }
      }
        
        fixboard(board,n,m);
        
    }
    
    static int countOnes (int [][] board, int row, int col)
    {
         int countOne = 0;
        
        //topleft
        if(row > 0 && col > 0){
            if(board[row-1][col-1] == 1 || board[row-1][col-1] == 3) countOne++;
        } 
        
        
        //top
        if(row > 0){
            if(board[row-1][col]== 1 || board[row-1][col] == 3) countOne++;
        }
        
        //topright
        if(row > 0 && col<board[0].length-1){
            if(board[row-1][col+1]== 1 || board[row-1][col+1] == 3) countOne++;
        }
        //left
        if(col > 0){
            if(board[row][col-1]== 1 || board[row][col-1] == 3) countOne++;
        }
        //right
        if(col < board[0].length -1){
            if(board[row][col+1]== 1 || board[row][col+1] == 3) countOne++;
        }
        //bottomleft
        if(row < board.length-1 && col > 0){
            if(board[row+1][col-1]== 1 || board[row+1][col-1] == 3) countOne++;
        }
        //bottom
        if(row < board.length-1){
            if(board[row+1][col]== 1 || board[row+1][col] == 3) countOne++;
        }
        //bottomright
        if(row < board.length-1 && col<board[0].length-1){
            if(board[row+1][col+1]== 1 || board[row+1][col+1] == 3) countOne++;
        }
        return countOne;
    }
    
    static void fixboard(int [][]board,int n, int m)
    {
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<m;j++)
            {
                if(board[i][j]==2)
                   board[i][j]=1;
                if(board[i][j]==3)
                   board[i][j]=0;
            }
        }
    }
}