PHP: finding the shortest solution for a recursive function

Question

I have tried to solve this problem: you are given two integers(A and B). You need to make an output from A to B(inclusively) in ascending order if A < B and in descending order if B < A. The problem is that it has to be done using a recursive function. I have come up with the following:

function showAB($a, $b) {
    if ($a > $b) {
        if ($a == $b) {
            return $a;
        } else {
            return $a . "<br>" . showAB($a - 1, $b);
        }
    } 
    else {
        if ($a == $b) {
            return $a;
        } else {
            return $a . "<br>" . showAB($a + 1, $b);
        }
    }
}

However, I was told that the solution to this problem can be done in 2 lines of code or less, so my question is about optimizing the function I already have.

"optimizing" isn't allways squeesing everything in 2 lines... There is code that can never be reached though (line 4) — Jeff
– Jeff, Commented Feb 26, 2019 at 23:29
beware of the word "optimizing". When looking at your code now, it's readable and easy to follow logically. An "optimized" solution with fewer lines of code may be a single function that has a single line of code: return ($a > $b) ? $a."<br>".showAB($a-1, $b) : ($a == $b) ? $a : $a."<br>".showAB($a+1, $b); I haven't tested this, but this should execute the same as the code above and is only a single line! But it's nowhere near as readable as what you have... — WOUNDEDStevenJones
– WOUNDEDStevenJones, Commented Feb 26, 2019 at 23:29
As @WOUNDEDStevenJones says, optimising often makes code a lot less readable. Here's a pretty simple version though: return ($a != $b) ? $a . '<br>' . showAB($a + ($a < $b ? 1 : -1), $b) : $a . '<br>'; 3v4l.org/bba8k — Nick
– Nick, Commented Feb 26, 2019 at 23:31
He has logic in his function what will never run like within his first if statement, $a will never == $b because if $a > $b they are obviously not equal to each other — Second2None
– Second2None, Commented Feb 26, 2019 at 23:40

Second2None · Accepted Answer · 2019-02-26 23:38:19Z

1

You can still optimise without making it look ugly, especially removing pointless logic. If you want a 1 liner then refer to the comments otherwise you can remove your else statements and it's still easy to read:

function showAB($a, $b) {
    if ($a < $b) {
        return $a . "<br>" . showAB($a + 1, $b);
    }
    if ($a > $b) {
      return $a . "<br>" . showAB($a - 1, $b);
    } 
    return $a;
}

answered Feb 26, 2019 at 23:38

Second2None

1,6201 gold badge15 silver badges24 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Pinke Helga · Accepted Answer · 2019-02-27 01:00:13Z

0

Golf? You could use the ternary operator ?..: and the 'spaceship' operator <=> giving -1/0/1 for less than/equal/greater than

function showAB(int $a, int $b) : string
{
  return $a . '<br>' . PHP_EOL . ($a === $b ? '' : showAB($a - ($a<=>$b), $b));
}

answered Feb 27, 2019 at 1:00

Pinke Helga

6,7622 gold badges25 silver badges46 bronze badges

1 Comment

Max Goryunov Over a year ago

I know what PHP_EOL does, but I would like to know why you decided to use it and is it necessary or not.

Collectives™ on Stack Overflow

PHP: finding the shortest solution for a recursive function

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related