Find total year spans in an array with gaps - php

Question

I need to draw a stacked bar graph for this array which should have 2 bars separated with a white-space of 2 years span (from year 1998 to 2000)
The Problem:
the first bar should be like,
*1998-1997* - *2 years gap* - *2000-2008*
The bars should merge shorter year-spans within like it did in taking 2000 from array0 and 2008 from array 1
Array
(
[comp_name] => C++
[parent_cat_name] => Information Technology
[sub_cat_name] => Programming
[total_years] => 6
[last_year] => 2006
[start_year] => 2000
)
Array
(
[comp_name] => .NET
[parent_cat_name] => Information Technology
[sub_cat_name] => Programming
[total_years] => 7
[last_year] => 2008
[start_year] => 2001
)
Array
(
[comp_name] => API
[parent_cat_name] => Information Technology
[sub_cat_name] => Programming
[total_years] => 1
[last_year] => 1998
[start_year] => 1997
)

Answer 1

You want to merge two array items, if they are adjacent according to some condition AND have some equality condition on some other fields.
You might do:
for(;;)
{
$merge = array();
$n = count($data);
for ($i = 0; empty($merge) && $i < $n-1; $i++)
{
for ($j = $i+1; empty($merge) && $j < $n; $j++)
{
// Are $i and $j congruent?
if ($data[$i]['parent_cat_name'] != $data[$j]['parent_cat_name'])
continue;
if ($data[$i]['sub_cat_name'] != $data[$j]['sub_cat_name'])
continue;
// Are $i and $j adjacent?
if ($data[$i]['last_year']+1 == $data[$j]['start_year'])
{
$merge = array($i, $j);
break;
}
if ($data[$j]['last_year']+1 == $data[$i]['start_year'])
$merge = array($j, $i);
break;
}
// They are congruent but not adjacent, try the next
}
}
// If we get to the end and find nothing mergeable, exit.
if (empty($merge))
break;
list($i, $j) = $merge;
// We add $j to $i
$data[$i]['last_year'] = $data[$j]['last_year']
$data[$i]['total_years'] += $data[$j]['total_years']
// We destroy $j
unset($data[$j]);
// Dirty renumber
$data = array_values($data);
// Now data has been modified, let's do this again.
}