Iterations issues in php

Question

I'm facing a problem that I can't solve ...

Here it is, I get from a HTML page a sudoku in this form for example :

<table cellspacing="0" cellpadding="0" class="sudoku">
        <tr>
          <td class="chiffe1">0</td>
          <td class="chiffe1">0</td>
          <td class="chiffe1">0</td>
        </tr>
        <tr>
          <td class="chiffe1">0</td>
          <td class="chiffe1">0</td>
          <td class="chiffe1">0</td>
        </tr>
        <tr>
          <td class="chiffe1">0</td>
          <td class="chiffe1">0</td>
          <td class="chiffe1">0</td>
        </tr>
      </table>

The problem is that the incrementation for a 2D Array should be like this to fill it :

0,0
0,1
0,2
1,0
1,1
1,2
2,0
2,1
2,2
0,4
0,5
0,6
1,4
1,5
1,6
2,4
2,5
2,6
0,7
0,8
0,9
1,7
1,8
1,9 ...

For a tab with a size of [9][9].

My probleme is that I already programmed all the function to solve it but I was filling it with that logic :

for($i=0;$i<9;$i++){
   for($j=0;$j<9;$j++){
       $tab[$i][$j]=$val;
   }
}

But it doesn't match at all, so all my results are wrong, and my problem is that I can't translate the logic order of the filling with mathematical algorithm.

Can someone help me to find the good iteration to initialize that sudoku ?

Thank you for your help and your attention.

Answer 1

You'll have to loop on a set of three rows and three columns at a time and shift $i and $j by the starting value of the set:

// sets of three for $i
for($iset=0; $iset<3; $iset++) {
    $istart=$iset*3;
    for($i=0;$i<3;$i++){
        // sets of three for $j
        for($jset=0; $jset<3; $jset++) {
            $jstart=$jset*3;
            for($j=0;$j<3;$j++){
                $tab[$istart+$i][$jstart+$j]=$val;
            }
        }
    }
}

So for sets (0, 1, 2) you'll have starting values (0, 3, 6). So you'll end up iterating through like this (which hopefully solves your problem):

i-> (0, 1, 2)   j -> (0, 1, 2), (3, 4, 5), (6, 7, 8)
i-> (3, 4, 5)   j -> (0, 1, 2), (3, 4, 5), (6, 7, 8)
i-> (6, 7, 8)   j -> (0, 1, 2), (3, 4, 5), (6, 7, 8)