This question already has an answer here:
I am trying to create this algorithm with PHP. I want to be able to echo out the result of this operation:
1 - 2 + 3 - 4 + 5 - 6 +...100
I want to get the result of this till I get to 100.
This how I have already started the code, however I am stuck and don't know how to proceed:
<?php
$somme = 0;
$I = 1;
while($I <= 100){
}
?>
How do I go on from this?
All answers are appreciated
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It's a case of knowing, within the loop, when to add and when to subtract. A simple tracker will help us here.
$somme = 0;
$i = 1;
$op = 'sub';
while($i <= 100){
$somme = $op == 'sub' ? $somme - $i : $somme + $i;
$op = $op == 'sub' ? 'add' : 'sub';
$i++;
}
As noted in the comments, you could also decide the operation based on whether $i is even or odd.