Thread: value in random slot of 2d array?

This is a large never ending project .. but a piece at this point is to:

currently I'm taking a random value from a text file.. There are 16 values grabbed and placed in a 2d array 4x4.

Currently I am storing statically through the below if/else statement. What I would like to do is randomly store those 16 values in a 2d array.

Code:

while(!feof(fid))
	{
		fscanf(fid, "%s", line);
		printf("%s\n", line);
		r = rand()%6;
		c = line[r];
		printf(" %c %d\n", c,r);
	        board[i][j]=c;

//****** insert values to board ******************
			if (i==3)
			{
				i=0;
				j++;
			}
	
			else
				i++;
		
	}  // end while
	
// ************ output values of board ***************
	for(i=0; i<4; i++)
	{
		 for(j=0; j<4; j++)
		{
			printf("%c\n",board[j][i]);
		}
	}

Originally Posted by DJPlayer

I randomly grabbed 16 values from a text file. Now I want to that those 16 random letters and randomly place them in a 2d array. Currently I'm putting them in a set pattern vs using rand().

Looking at your code, it seems that your random selection involves selecting 1 of the first 6 characters in the current line. This means that someone who knows the contents of the file has about a 1/6 chance of correctly guessing the value of a given array element.

What you can do is shuffle the 2D array: select an element at random from the array, then swap it with the first element (presumably board[0][0]). Then excluding the new first element, select an element at random from the array, then swap it with the second element (e.g., board[0][1]). Repeat for the third until the last element, each time excluding the elements in positions that have already been processed.