Program that prints star pattern

Question

I have a program that prints the star pattern.

Starr Pattern is:

 * 
 * 
 * 
 * 
 * * * * * * * * * 
 * 
 * 
 * 
 * 

My code is:

$n=5;
for($i=0; $i<$n; $i++){
 for($k=$n-$i; $k>0; $k--){
 echo ' '.' ';
 }
 for($j=0; $j< ($tot = $i+1); $j++){
 if($i==$j && $tot<$n){
 echo '* ';
 }else{
 if($tot<$n){
 echo ' '.' '; 
 }else{
 echo '* ';
 }
 }
 }
 if($i == ($n-1)){
 for($l=$n-1; $l>0;$l--){
 echo '* '; 
 }
 } 
 echo '<br/>';
}
for($i=0;$i<$n;$i++){
 for($k=$n-$i; $k>0; $k--){
 echo ' '.' ';
 }
 for($j=0; $j< ($tot = $i+1); $j++){
 if($i==$j && $tot<$n){
 echo '* ';
 }else{
 echo ' '.' '; 
 }
 }
 echo '<br/>';
}

My question is that how can I calculate the complexity of this code?

And also Is there a good way to reduce loops?

• ArtisticPhoenix: Looks like a Plus + to me, guess it's just semantics....
• ArtisticPhoenix: good way to reduce loops yes str_repeat and chunk_split you can see this example (a code golf answer I did) of what you can do with these 2, codegolf.stackexchange.com/questions/171679/… basically you could make one long string with the space or * by using str_repeat and then split it into rows with chunk_split
• Gufran Hasan: Thanks, @ArtisticPhoenix, I have seen it but didn't get any logic because of the code in a single line.
• ArtisticPhoenix: For example function f($n){$s='';$b=str_pad('*',($m=$n*2+1),' ',2);for($i=0;$i<$m;++$i)$s.=($i==$n)?str_repeat('*',$m):$b;return chunk_split($s, $m);} Sandbox
• Gufran Hasan: It looks nice. Can you please make me understand how it works.

Answer 1

It looks nice. Can you please make me understand how it works

For example

 function f($n){$s='';$b=str_pad('*',($m=$n*2+1),' ',2);for($i=0;$i<$m;++$i)$s.=($i==$n)?str_repeat('*',$m):$b;return chunk_split($s, $m);}

Output

 * 
 * 
 * 
 * 
 * 
***********
 * 
 * 
 * 
 * 

Sandbox

Let me write it in a way that is easier to see

$n = 5;
$row_len = $n*2+1;
$output = '';
//pad $n spaces on each side of *
$default = str_pad('*',$row_len,' ',STR_PAD_BOTH); //is = " * "
//loop once for each vertical row (same as width)
for($i=0;$i<$row_len;++$i){
 if($i==$n){
 //do the center line all *'s
 $output .= str_repeat('*',$row_len);//is = "***********"
 }else{
 //use the default line from above
 $output .= $default;
 }
}
//now we have a single line that is the length squared so we can chunk it
//into equal parts, to make a square
echo chunk_split($output, $row_len); //is = " * * ***********"

Sandbox

Basically we can create the " * " row by using string pad. Because we can pad spaces on both sides of a * up to the length of a row ($n*2)+1.

Then the center row, is just * so we can use string repeat to the length of the row for that line.

Last we take our big huge line of spaces and * and split it into chunks (\n) on the length of our row we want.

• ArtisticPhoenix: Hope that helps explain it a bit better. Basically were exploiting the fact that it conforms to a set pattern. So for example we know if $n is 5 to do 5 spaces a star and 5 more spaces ($n*2)+1 So we can just use String Pad for that and pad 5 spaces on each side. String Pad takes the total length of the string you want. So it's the full length of the row.
• mickmackusa: I think your output is skinnier than the OPs.
• ArtisticPhoenix: @mickmackusa - it is. I didn't put a space between * * the stars. Shouldn't be too hard to fix, but it adds a variable in. So I was too lazy .... lol
• mickmackusa: DEREGISTERED!!!! What have you done, you mad man! What causes a person to do that?!? An occupational requirement? Witness protection?

Answer 2

Here's my array-functional spin on the task. It is not likely to be faster than @ArtisticPhoenix's solution, but it provides the desired output without loop constructs or conditions. ...just different for the sake of being different.

The process generates a full-sized array of strings that "looks" like a vertical stroke of asterisks, then replaces the middle element with a horizontal stroke element.

Code: (Demo)

$size = 7; // circumference not radius 
$vertical = str_pad('*', $size * 2 - 1, ' ', STR_PAD_BOTH); // row w/ central symbol
$result = array_fill(0, $size, $vertical); // top-to-bottom stroke of symbols
$result[$size / 2] = implode(' ', array_fill(0, $size, '*')); // left-to-right stroke of symbols
echo implode(PHP_EOL, $result);

For improved readability, I've declared the single-use variable $vertical.

Output: (highlight the text with your cursor to see that the pattern has no unnecessary trailing spaces in any line.)

 * 
 * 
 * 
* * * * * * *
 * 
 * 
 * 

*notice that I am not bothering to floor() the "horizontal stroke" element key, because php casts float keys to integers. https://www.php.net/manual/en/language.types.array.php