Question

Hey! I'm stuck with this task from the Princeton course on Coursera.

Write a program Minesweeper.java that takes three integer command-line arguments m, n, and k and prints an m-by-n grid of cells with k mines, using asterisks for mines and integers for the neighboring mine counts (with two space characters between each cell). To do so,
Generate an m-by-n grid of cells, with exactly k of the mn cells containing mines, uniformly at random.
For each cell not containing a mine, count the number of neighboring mines (above, below, left, right, or diagonal).

I don't really know how to place the mines randomly in the two dimensional array that is the grid, nor how to count the number of neighbouring mines. I've been stuck for days now. Could someone help?

Answer 1

Hello here is the code for the above problem. Hope it helps. I have added comments for better understanding. If you are satisfied with the answer, do consider upvoting!

Minesweeper.java

import java.util.Random;
import java.util.Scanner;

public class Minesweeper {
  
   //returns true if the point is within bounds and has arr has '*' as value at that x,y.
   public static boolean issafe(char arr[][],int x,int y,int n,int m)
   {
       return x>=1 && x<=n && y>=1 && y<=m && arr[x][y] == '*';
   }
  
   //finds number of neighbours which are '*'.
   public static int findNeighbours(char arr[][],int x,int y,int n,int m)
   {
       int count = 0;
       if(issafe(arr,x-1,y,n,m))
           count++;
       if(issafe(arr,x-1,y+1,n,m))
           count++;
       if(issafe(arr,x,y+1,n,m))
           count++;
       if(issafe(arr,x+1,y+1,n,m))
           count++;
       if(issafe(arr,x+1,y,n,m))
           count++;
       if(issafe(arr,x+1,y-1,n,m))
           count++;
       if(issafe(arr,x,y-1,n,m))
           count++;
       if(issafe(arr,x-1,y-1,n,m))
           count++;
       return count;
   }
   public static void main(String[] args) {
       //using reader to take n,m,k as input;
       Scanner reader = new Scanner(System.in);
       //used to generate random numbers.
       Random r = new Random();
      
       System.out.println("Enter n");
       int n = reader.nextInt();
      
       System.out.println("Enter m");
       int m = reader.nextInt();
      
       System.out.println("Enter k");
       int k = reader.nextInt();
      
       //defining 2-d matrix arr[1-n][1-m];
       char arr[][] = new char[n+1][m+1];
       int tmp = k;
       int row_num = r.nextInt(n) + 1;
       int column_num = r.nextInt(m) + 1;
      
       //generating k mines randomly.
       while(tmp>0)
       {
           //keep generating row and column numbers till the time we have
           //a position which does not contain '*'.
           while(arr[row_num][column_num]=='*')
           {
               //generates random number between [1-n].
               row_num = r.nextInt(n)+1;
               //generates random number between [1-m].
               column_num = r.nextInt(m)+1;
           }
           //setting generated position as '*'.
           arr[row_num][column_num] = '*';
           tmp--;
       }
       for(int i=1;i<=n;i++)
       {
           for(int j=1;j<=m;j++)
           {
               if(arr[i][j]!='*')
               {
                   //function returns the number of neighbours which are '*';
                   int count = findNeighbours(arr,i,j,n,m);
                   //converts the number to char value. Ex: 2 is converted to '2';
                   arr[i][j] = (char)(count+48);
               }
           }
       }
      
       //printing the resulting 2-d matrix.
       System.out.println("Final result:");
       for(int i=1;i<=n;i++)
       {
           for(int j=1;j<=m;j++)
           {
               System.out.print(arr[i][j]+" ");
           }
           System.out.println();
       }
   }

}

OUTPUT: