Question

My apologies if this is the wrong site for this problem, as it is more math-related than programming.

I am trying to write a series of 7 page links, in a Google-esque fashion. Essentially, it will be 7 numbers, s to (s + 6), where s is my starting value. I am having trouble calculating my starting value, given a limited amount of information.

In advance, I know the maximum value in the series, this is variable, but it is always greater than 7. In my formula-writing attempts, I have been calling this value g, so g > 7.

I also know the page number the user has selected. I have been calling this value p

So, for example, if g was 8, I would need to generate these series of numbers, where the bolded number is equal to p:

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

1 2 3 4 5 6 7

2 3 4 5 6 7 8

2 3 4 5 6 7 8

2 3 4 5 6 7 8

2 3 4 5 6 7 8

As long as I can determine the starting value using the information available, everything else falls into place. Can anyone advise on how I would calculate my starting value using the information available? If it is relevant, I will be writing this formula in PHP.

Thanks in advance for any input.

Answer 1

This is just simulation code for testing.

<?
$g=16;
for($p=1;$p<17;$p++){
$start = $g-$p > 3 ? ($p-4<1?1:($p-4)) : $g-6;
    echo "$p :: ";
    for($i=$start;$i<$start+7;$i++){
        echo $i . " ";
    }
    echo "<br>";
}
?>

SO your Start Page is decided by (the thing you actually need):

$start = $g-$p > 3 ? ($p-4<1?1:($p-4)) : $g-6;

Output (Simulation for g=16, and p from 1 to 16)::

p :: page numbers

1 :: 1 2 3 4 5 6 7
2 :: 1 2 3 4 5 6 7
3 :: 1 2 3 4 5 6 7
4 :: 1 2 3 4 5 6 7
5 :: 1 2 3 4 5 6 7
6 :: 2 3 4 5 6 7 8
7 :: 3 4 5 6 7 8 9
8 :: 4 5 6 7 8 9 10
9 :: 5 6 7 8 9 10 11
10 :: 6 7 8 9 10 11 12
11 :: 7 8 9 10 11 12 13
12 :: 8 9 10 11 12 13 14
13 :: 10 11 12 13 14 15 16
14 :: 10 11 12 13 14 15 16
15 :: 10 11 12 13 14 15 16
16 :: 10 11 12 13 14 15 16

And simulation for g=8, p from 1 to 8

1 :: 1 2 3 4 5 6 7
2 :: 1 2 3 4 5 6 7
3 :: 1 2 3 4 5 6 7
4 :: 1 2 3 4 5 6 7
5 :: 2 3 4 5 6 7 8
6 :: 2 3 4 5 6 7 8
7 :: 2 3 4 5 6 7 8
8 :: 2 3 4 5 6 7 8