CODEWITHSUNDEEP
loopsfor-loop
varunkumar
varunkumar

Reputation: 340

Which for loop format to use here?

Recently I had an interview in which I was asked to make a output of the following kind:

 9
 1
 8
 2
 7
 3
 6
 4

Now I hadn't practiced much but somehow managed to make this . In which i use 2 variables $i($i=1) and $num($num=9). And make the condition $i<5 and increase it by one till it reaches 5.

<?php
$num=9;
for($i=1;$i<5;$i++) {
    echo $num . "<br>". $i."<br>";
    $num--;
}
?>

Which gives the output I require. But there another way of doing it by using $i and $j as the variables. So I want to know which one is simpler and better.

<?php 
for($i=1,$j=9; $j>=6; $i++,$j--){
    echo($j."<br/>".$i."<br />");
}
?>

Upvotes: 1

Views: 135

Answers (4)

Heroselohim
Heroselohim

Reputation: 1291

One variable solution

for($i=1; $i<5; $i++) {
    echo 10 - $i . "<br>". $i."<br>";
}

Upvotes: 1

Chris Haas
Chris Haas

Reputation: 55457

More generically this can be written as:

<?php
//Bounds
$upper = 9;
$lower = 1;

//Mid-point, use MOD 2 to add 1 for odd numbers
$mid = ( $upper + ( $upper % 2 ) ) / 2;


for( $i = $lower, $j = $upper; $i <= $mid && $j > $mid; $i++, $j-- )
{
    echo $j;
    echo "\n";
    echo $i;
    echo "\n";
}

It gets a little vague towards the end of the sequence. The sequence that you provided completely ignores the center/pivot number (5) and the above code does the same for an odd range of numbers but shows them for even ranges. If the goal is to always ignore the center one or two (odd or even) then you can change the second center condition in the for loop:

for( $i = $lower, $j = $upper; $i < $mid && $i !== $j; $i++, $j-- )
{
    echo $j;
    echo "\n";
    echo $i;
    echo "\n";
}

Upvotes: 1

johng
johng

Reputation: 11

I think it would be preferable to run a loop that decrements from 9 and use a variable to track the number of iterations:

$count = 0;

for ($i = 9; $i >= 6; $i--)
{
    $count++;
    echo $i."\n";
    echo $count."\n";
}

Upvotes: 1

Mihail Petkov
Mihail Petkov

Reputation: 1545

This looks better for me

for ($i=1, $j=9; $i<5; $i++,$j--) {
  echo $j;
  echo "\n";
  echo $i;
  echo "\n";
}

Upvotes: 1

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