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2D Array Search

connork
connork asked
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Last Modified: 2010-04-10
Hi!

Working on what to everyone else is a simple program but to me is proving quite difficult.  Program simulates birth and death within a two dimensional array.

Specifically, after the user specifies that life exists in say seven elements, successive generations are displayed using these two rules:

1) an organism in a cell survives to the next generation if exactly 2 or 3 of its neighbors are living, otherwise it dies

2) an organism is born into an unoccupied cell if exactly 3 of its neighbors are unoccupied.

Obviously I'm a student and I don't even know where to begin writing what is probably a series of loops to search for values in the six surrounding elements.

Would someone please show me what this code would look like and explain the why of it?

Thanks much.

Keith Connor

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For any current cell, located at position i, j, the following
loops count the number of living and dead cells:

nof_dead= 0;
nof_alive= 0;

for (di= -1; di <= 1; di++)
   for (dj= -1; dj <= 1; dj++)
      if (cell[i+di][j+dj] == dead)
         nof_dead++;
      else
         nof_alive++;

Now determine what to do with the current cell:

if (cell[i][j] == alive) {
   if (nof_alive == 2 || nof_alive == 3)
      next_cell[i[[j]= alive;
   else
      nex_cell[i][j]= dead;
}
else if (nof_alive == 3)
   next_cell[i][j]= alive;
else
   next_cell[i][j]= dead;

The array nex_cell contains the next generation of
all the cells ...

does this clarify things a bit?

kind regards,

Jos aka jos@and.nl

ps. Note that some care has to be taken for 'wrap around',
     i.e. the cells next to the border of the array must be taken
     care of in a sensible way. The normal approach is to
    define the cell array as a torus, i.e. the rightmost cells
    have the leftmost cells as their right neighbors etc.

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Commented:
Jos,

Thanks!  Of course being a student I'm going to have to 'digest'
this :).  Also, for clarification this will only provide the results of one cell or all?

Keith Connor
 


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