LifeGame.java

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

/*Pratik*/

class Solution {
    public void gameOfLife(int[][] board) 
    {
        if(board==null || board.length==0 || board[0].length==0)return;
        for(int i=0;i<board.length;i++)
        {
            for(int j=0;j<board[0].length;j++)
            {
                
                int count = 0;
                if(isAlive(board,i-1,j))count++;
                if(isAlive(board,i,j-1))count++;
                if(isAlive(board,i-1,j-1))count++;
                if(isAlive(board,i-1,j+1))count++;
                if(isAlive(board,i+1,j))count++;
                if(isAlive(board,i+1,j-1))count++;
                if(isAlive(board,i+1,j+1))count++;
                if(isAlive(board,i,j+1))count++;
                if(board[i][j]==1)
                {
                    if(count>3 || count<2)
                    {
                        board[i][j] = 3;
                    }
                    else if(count==2 || count==3)
                    {
                        board[i][j] = 1;
                    }
                }
                else 
                {
                    if(count==3)
                    {
                        if(board[i][j]==0)board[i][j] = 2;
                    }
                }
            }
        }
        for(int i=0;i<board.length;i++)
        {
            for(int j=0;j<board[0].length;j++)
            {
                if(board[i][j]==3)board[i][j] = 0;
                else if(board[i][j]==2)board[i][j] = 1;
            }
        }
    }
    public boolean isAlive(int[][] board,int i,int j)
    {
        if(i<0 || j<0 || i>=board.length || j>=board[0].length)
        {
            return false;
        }
        if(board[i][j]==1|| board[i][j]==3)return true;
        return false;
    }
}

/*Prateekshya*/
/*Brute Force*/

class Solution {
    public void gameOfLife(int[][] board) {
        int[][] result = new int[board.length][board[0].length];
        for (int i = 0; i < board.length; ++i)
        {
            for (int j = 0; j < board[0].length; ++j)
            {
                int neighbourCount = 0;
                if (i > 0 && board[i-1][j] == 1) ++neighbourCount;
                if (i < board.length-1 && board[i+1][j] == 1) ++neighbourCount;
                if (j > 0 && board[i][j-1] == 1) ++neighbourCount;
                if (j < board[0].length-1 && board[i][j+1] == 1) ++neighbourCount;
                
                if (i > 0 && j > 0 && board[i-1][j-1] == 1) ++neighbourCount;
                if (i > 0 && j < board[0].length-1 && board[i-1][j+1] == 1) ++neighbourCount;
                if (i < board.length-1 && j > 0 && board[i+1][j-1] == 1) ++neighbourCount;
                if (i < board.length-1 && j < board[0].length-1 && board[i+1][j+1] == 1) ++neighbourCount;
                
                if (neighbourCount < 2) result[i][j] = 0;
                else if (neighbourCount == 3) result[i][j] = 1;
                else if (neighbourCount == 2 && board[i][j] == 1) result[i][j] = 1;
                else if (neighbourCount > 3) result[i][j] = 0;
            }
        }
        for (int i = 0; i < board.length; ++i)
            for (int j = 0; j < board[0].length; ++j)
                board[i][j] = result[i][j];
    }
}

/*In place solution*/

/*
1->0 = -2
0->1 = -1
*/


class Solution {
    public void gameOfLife(int[][] board) {
        for (int i = 0; i < board.length; ++i)
        {
            for (int j = 0; j < board[0].length; ++j)
            {
                int neighbourCount = 0;
                if (i > 0 && (board[i-1][j] == 1 || board[i-1][j] == -2)) ++neighbourCount;
                if (i < board.length-1 && (board[i+1][j] == 1 || board[i+1][j] == -2)) ++neighbourCount;
                if (j > 0 && (board[i][j-1] == 1 || board[i][j-1] == -2)) ++neighbourCount;
                if (j < board[0].length-1 && (board[i][j+1] == 1 || board[i][j+1] == -2)) ++neighbourCount;
                
                if (i > 0 && j > 0 && (board[i-1][j-1] == 1 || board[i-1][j-1] == -2)) ++neighbourCount;
                if (i > 0 && j < board[0].length-1 && (board[i-1][j+1] == 1 || board[i-1][j+1] == -2)) ++neighbourCount;
                if (i < board.length-1 && j > 0 && (board[i+1][j-1] == 1 || board[i+1][j-1] == -2)) ++neighbourCount;
                if (i < board.length-1 && j < board[0].length-1 && (board[i+1][j+1] == 1 || board[i+1][j+1] == -2)) ++neighbourCount;
                
                if (neighbourCount < 2)
                {
                    if (board[i][j] == 1)
                        board[i][j] = -2;
                }
                else if (neighbourCount == 3)
                {
                    if (board[i][j] == 0)
                        board[i][j] = -1;
                }
                else if (neighbourCount > 3)
                {
                    if (board[i][j] == 1)
                        board[i][j] = -2;
                }
            }
        }
        for (int i = 0; i < board.length; ++i)
            for (int j = 0; j < board[0].length; ++j)
                board[i][j] = board[i][j] == -2 ? 0 : (
                                board[i][j] == -1 ? 1 : board[i][j]);
    }
}