The Task

You’ve one array with tickets of linked destinations – so you start from one city to another, than next and so on. Each element is an array with “from” and “to” destinations:

$inputTickets = array(
    0 => array('from' => 'barcelona', 'to' => 'madrid'),
    1 => array('from' => 'sofia', 'to' => 'paris'),
    2 => array('from' => 'madrid', 'to' => 'milano'),
    3 => array('from' => 'paris', 'to' => 'barcelona'),
    4 => array('from' => 'cupertino', 'to' => 'sofia'),
    5 => array('from' => 'milano', 'to' => 'valencia'),
    6 => array('from' => 'valencia', 'to' => 'nice'),
    7 => array('from' => 'mountain view', 'to' => 'cupertino'),
);

It’s easy to construct two arrays – the “from” destinations array and the “to” destinations array, and here the easiest way to get the starting point of the whole trip, because of the fact that these are linked tickets.

$fromDestinations = $toDestinations = array();

foreach ($inputTickets as $k => $v) {
    $fromDestinations[] = $v['from'];
    $toDestinations[]   = $v['to'];
}

// and finally get the starting point
$startPoint = array_diff($fromDestinations, $toDestinations);

Conclusion

Beside of knowing several algorithm techniques, there’s also need of knowing the language syntax and possibilities – in that case PHP’s

Recently I wrote about list() in PHP which is indeed very powerful when assigning variable values from array elements.

$a = array(10, array('here', 'are', 'some', 'tests'));
list($count, $list) = $a;

Actually my example in the post was not correct, because I wrote that you can pass an associative array, but the truth is that you cannot, and thus the array should be always with numeric keys. After noticing the comments of that post, and thanks to @Philip,  I searched a bit about how this problem can be overcome.

There is a Solution

As always PHP gives a perfect solution! You can see on the list() doc page that there is a function that may help you use an associative array.

Extract

extract() is perhaps less known than list(), but it does the right thing!

$a = array('count' => 10, 'list' => array('here', 'are', 'some', 'tests'));
extract($a);

echo $count;    // 10
print_r($list); // array('here'....

Note that now both $count and $list are defined.

My advice is to rely on a defined standard. I personally use the Zend Framework’s coding style.

So how to format the code? The first way is on the same line:

$myArray = array('key1' => 'value1',
		 'key2' => 'value2');

And the other, perhaps more clear way is to place the associative pairs on a new line:

$myArray = array(
	'key1' => 'value1',
	'key2' => 'value2',
);

Note that in the second example there’s a comma after the second pair. This is correct PHP syntax and is strongly encouraged!

It’s up to you which way to take. However it mainly depends on the case, but please use standards.

Actually there aren’t so many array functions in JavaScript. As you know you can join, sort, etc. which methods are pretty basic. What I’d like to do is something similar to PHPs’ array_merge and than array_unique.

With JavaScript that seems pretty impossible. You can merge them with the .concat function as in the example bellow:

var a = [1,2];
var b = [3,4];
a.concat(b);

this gives you array with four elements. But when it comes to trim all the duplicates as it’s array_unique in PHP, well that’s really impossible. You’ve to do it by yourself, and I don’t thing this is the best technique. That slows down the code and you should avoid it!

There are two ways to make new instance of a JavaScript array. As the previous sentence says one of them is by using the new operator. Actually even if you’re not familiar with JavaScript you’ve probably heart something about “new” from some other programming language, as it is very common to appear in almost every one. The way you make new instance is simply by:

var arr = new Array();

That seems pretty natural. The other way to make new instance, probably with some basic initialization is by using:

var arr = [];
// or if you'd like to put some predefined
// values into the array
// on init time
var arr = ['val1','val2'];

The reason I write this post is because as it seems the second way to instantiate an array in JavaScript is faster. That even if it seems funny is really important, because in modern, cool sites there’s a lot of JavaScript and probably there are thousands of “new Array()”‘s which replaced by the simple “arr = []” may result in faster and more user fiendly site!

So use:

var arr = [];