bad array value in loop

Question

I am trying this loop, but i have a problem in $m[2][3]. None value is showed. So i have some problem with increments.

$nArr = array('A', 'B', 'C', 'D', 'E', 'F');

$lp = 4;

for ($i = 0; $i < $lp; $i++) {
    $m[$i][$i] = 1;
    for ($x = $i; $x < $lp; $x++) {
        $v = $i+$i;
        $m[$i][$x+1] = $nArr[$x+$v];
    }
}

this is my output :

1 + A + B + C + - 1 + D + E + - 1 +   + - 1 +

The output that i want:

1 + A + B + C + - 1 + D + E + - 1 + F + - 1 +

in detail:

echo $m[0][0]."+"; 1
echo $m[0][1]."+"; A
echo $m[0][2]."+"; B
echo $m[0][3]."+"; C
echo " - ";
echo $m[1][1]."+"; 1
echo $m[1][2]."+"; D
echo $m[1][3]."+"; E
echo "- ";
echo $m[2][2]."+";1
echo $m[2][3]."+"; //error, must be F
echo "- ";
echo $m[3][3]."+"; 1

Galled · Accepted Answer · 2011-10-28 00:35:40Z

2

Your problem is in your progression. In the second "for" your progression increases rapidly:

$v = $i+$i;         
$m[$i][$x+1] = $nArr[$x+$v];

In the first iteration starts with 0 + 0 + 0 ($ x + $ i + $ i) = 0 = "A"
In the second iteration begins with 1 + 1 + 1 ($ x + $ i + $ i) = 3 = "D"
and the third iteration begins with 2 + 2 + 2 ($ x + $ i + $ i) = 6 = null, your array has 6 elements so your max index is 5.

You should change the progression in order to get the next progression of indexes: 0, 3, 5.

Try this:

$nArr = array('A', 'B', 'C', 'D', 'E', 'F');
$lp = 4;                
for ($i = 0; $i < $lp; $i++) {
     $m[$i][$i] = 1;            
    for ($x = $i; $x < $lp; $x++) {                
        $v = $i+ceil($i/2);
        $m[$i][$x+1] = $nArr[$x+$v];            
    }        
}

edited Oct 28, 2011 at 0:35

answered Oct 28, 2011 at 0:21

Galled

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1 Comment

Daniel Over a year ago

1+B+C+D+ - 1+D+E+- 1+F+- 1+ << output

Mike Purcell · Accepted Answer · 2011-10-28 00:38:49Z

1

Lol, had to accept the challenge...

$nArr = array('A', 'B', 'C', 'D', 'E', 'F');

$counter = 3;

while ($counter > 0) {    

    $chunkedValues[$counter][0] = 1;

    for ($j = 0 ; $j < $counter ; $j++) {
        $chunkedValues[$counter][$j + 1] = $nArr[$j];
    }

    $nArr = array_slice($nArr, $counter--);
}

var_dump($chunkedValues);

answered Oct 28, 2011 at 0:38

Mike Purcell

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Comments

Ariel · Accepted Answer · 2011-10-27 23:58:19Z

0

$lp is 4, I bet it should be 5. Or even better set it to count($nArr) - 1.

PS. What in the world is this loop for?

Edit: Never mind, that didn't solve it.

answered Oct 27, 2011 at 23:58

Ariel

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Comments

ruakh · Accepted Answer · 2011-10-28 00:20:03Z

0

The problem is that your algorithm is wrong. Your code sets m[i][j] =

undefined if j < i
1 if j = i
nArr[2 * i + j - 1] if j > i

So m[2][3] = nArr[6], which is undefined.

It's not totally clear to me what you're trying to do, or why, but my best guess is this:

$nArr = array('A', 'B', 'C', 'D', 'E', 'F');

$lp = 4;

$nArr_index = 0;
for ($i = 0; $i < $lp; $i++) {
    $m[$i][$i] = 1;
    for ($j = $i + 1; $j <= $lp; $j++) {
        $m[$i][$j] = $nArr[$nArr_index++];
    }
}

answered Oct 28, 2011 at 0:20

ruakh

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1 Comment

Daniel Over a year ago

1+A+B+C+ - 1+E+F+- 1++- 1+ <<< output

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