Make pattern of asterisks and zeros in increasing lengths - php

Question

I'm trying to echo stars and zero like the pattern below
*
***0
******00
**********000
The length of the asterisks grows by an increasing factor (in a ballooning fashion) -- the previous number of asterisks plus the current iteration number.
iteration 1: 1 (0 + 1)
iteration 2: 3 (1 + 2)
iteration 3: 6 (3 + 3)
iteration 4: 10 (6 + 4)
iteration 5: 15 (10 + 5)
etc
The length of the zeros increases by a static factor.
iteration 1: 0
iteration 2: 1
iteration 3: 2
iteration 4: 3
iteration 5: 4
etc
My code currently looks like this:
for ($i=0; $i<=10; $i++)
{
echo "*";
for ($j=0; $j<$i; $j++)
{
echo "*";
}
for ($z=0; $z<$i; $z++)
{
echo "0";
}
echo "</br>";
}
However I'm getting this result:
*
**0
***00
****000
*****0000
******00000

Answer 1

The number of stars is indicated by triangle numbers, 1, 1+2, 1+2+3. You want to increment your inner loop max value by $i with every iteration:
$k = 0;
for ($i=1; $i<=10; $i++)
{
$k += $i;
for ($j=1; $j<=$k; $j++)
{
echo "*";
}
...
}
This is also a good case where your loops should be initialized with 1 rather than 0, because it is more intuitive. 0-based loops work best when you are working with arrays.

Answer 2

I think something like this is more efficient; you can cache the current sequence of stars and zeros.
$cache_star = "";
$cache_zero = "";
for ($i=1; $i<=10; $i++)
{
for ($j=1; $j<=$i; $j++)
{
$cache_star .= "*";
}
echo $cache_star.$cache_zero;
$cache_zero .= "0";
}

Answer 3

Here's what I got:
for($i = 1; $i != 5; $i++)
{
$triangle = (0.5 * $i) * ($i + 1);
echo str_repeat('*', $triangle) . str_repeat('0', $i) . PHP_EOL;
}
Uses the formula 0.5n(n + 1) - the triangle numbers formula.
Example output:
*0
***00
******000
**********0000

Answer 4

I quite like #jordandoyle's approach, but I correct the zeros pattern by subtracting 1 from $i in the second str_replace()..
Code: (Demo)
$number = 5;
for ($i = 1; $i <= $number; ++$i) {
echo str_repeat('*', $i * .5 * ($i + 1))
. str_repeat('0', $i - 1)
. PHP_EOL;
}
Output:
*
***0
******00
**********000
***************0000
If this answer lacks significant uniqueness versus an earlier answer, I'll include a recursive approach as well (instead of a classic loop).
Code: (Demo)
function printLines($i, $lines = [], $newline = PHP_EOL) {
if ($i > 0) {
array_unshift(
$lines,
str_repeat('*', $i * .5 * ($i + 1))
. str_repeat('0', $i - 1)
);
printLines(--$i, $lines);
} else {
echo implode($newline, $lines);
}
}
printLines(5);
You can even copy the previous line and insert it into the middle of the next line to form the desired pattern. This is the functional-style equivalent of #CoertMetz's nested loop technique.
Code: (Demo)
$number = 5;
$line = '';
for ($i = 1; $i <= $number; ++$i) {
echo (
$line = str_repeat('*', $i)
. $line
. ($i > 1 ? '0' : '')
)
. PHP_EOL;
}
All above techniques deliver the same result.

Answer 5

Smells like homework... But ok, what about this:
$star = "*";
echo $star."\n";
for ($i=0; $i<=10; $i++)
{
$star = $star."**";
echo $star;
echo str_repeat("0", $i+1);
echo "\n";
}
Outcome:
*
***0
*****00
*******000
*********0000
***********00000
*************000000
***************0000000
*****************00000000
*******************000000000
*********************0000000000
***********************00000000000
Demo:
http://sandbox.onlinephpfunctions.com/code/583644f782005adb9e018b965cbbdefaf63c7c79