array values all possible combinations

screenShot

How do I go about creating a recursive function that returns all combination sets of all array values from an array?
e.g.

$myArray = array(3,5,7,8);

I want all of these as output:

3,5,7,8
3,5,8,7
3,7,5,8
3,7,8,5
3,8,5,7
3,8,7,5
5,3,7,8
5,3,8,7
... etc.....

Thanks,
Vin

bradgrafelman

Do you know how to do it yourself? In other words, if you were given those four numbers, a pencil, and a piece of paper, would you be able to construct the correct answer?

If so, just break down the mental process that you would go through and convert each step into PHP code. There's your answer.

If not, then your problem isn't really a lack of PHP knowledge. Still, you could always just search for an existing solution.

screenShot

Yes on paper I can do it. That's not a problem. And the total number to the power of the same number will also give all combinations.
But I am getting into problems of endless loops and sorting issues. if i take the first number and for the remaining numbers two-sort orders of Ascending/Descending will give me few combinations. It's the in between ones I can't handle properly.

screenShot

correction: And the total number to the power of 2 should give all combinations

johanafm

screenShot;11036435 wrote:
correction: And the total number to the power of 2 should give all combinations

For N repeated draws out of a collection of 2.

For example, there are N² possible outcomes when flipping a coin N times.

You are looking at possible permutations of a collection of size N which is a different matter. If you have 3 items, you may choose the first item in three different ways. Then you may choose the second item in 2 different ways. Finally you may choose the last item in 1 different ways

3 * 2 * 1 = 6 = 3!

Or more generally, the first item can be selected in N ways, the second in N-1 ways, …, 2 ways, 1 way

N * (N-1) * (N-2) * … * 2 * 1 = N!

The easiest way of solving this is probably using recursion and an accumulator: permutationBuilder(accumulator, collection)

What have you tried so far? If you end up with infinite recursion you are probably missing an appropriate end condition, or you are not reducing the collection properly.