How could i shorten my for loop code?

I made a script to print out a diamond, but would like to make my script shorter. Only for loops are allowed. Is there a different logical way that could eliminate some for loops?

Here is the code:

 row=input('enter an odd number: \n');
for i= 1:ceil(row/2);
     for j=1:row-i
       fprintf(' ')
     end
     for k=1:2*i-1
       fprintf('*')
     end
    fprintf('\n') 
end  
for j=ceil(row/2)-1:-1:1
    for q=1:row-j
       fprintf(' ')
     end
    for         k=2*j-1:-1:1
       fprintf('*')
    end
     fprintf('\n') 
end
%this is what it prints:
row= 9     
    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

Also, the index logic could probably be simpler. Thanks!

Answer 1

[José-Luis]

numRows = 25
numStars = [1:2:numRows,numRows-2:-2:1];
numSpaces = (numRows - numStars) / 2;

If you really want a loop:

for (ii = [numStars;numSpaces])
    spacePrint = repmat(' ',1,ii(2));
    starPrint = repmat('*',1,ii(1));
    fprintf([spacePrint,starPrint,'\n']);
end

[Dan Po]

That works. Would you know if there is a way to merge the two ' * * ' sections in the code? I am at a beginners point of thinking, and am scrubbing my newbie brain for a solution, but have come short.

What I did was print line by line of spaces and *, and print line by line with the loop.

Also, at what point did you learn the tools for this solution method?

So far what I am not familiar with is repmat, ii, and organizing matrices like you did, but I will look into those things.

Thanks for your time.

for i= 1:ceil(row/2);
       for j=1:row-i
     fprintf(' ')
**     end
**     for k=1:2*i-1
     fprintf('*')
       end
  fprintf('\n') 
end  
for j=ceil(row/2)-1:-1:1
       for q=1:row-j
     fprintf(' ')
**     end
**     for         k=2*j-1:-1:1
     fprintf('*')
       end
   fprintf('\n') 
end

[José-Luis]

My pleasure. Seeing (and trying to understand) how other people do it is a good way to learn. I guess that's how I learned most of what I know now. It just takes time.

In don't understand what you mean by merge the two sections.

[Dan Po]

What i meant is is there a way to consolidate these two for loops (the starred lines)?

 for i= 1:ceil(row/2);
*         for j=1:row-i      %used to print spaces on one line
*     fprintf(' ')
*         end
*         for k=1:2*i-1      %used to print stars on same line
*     fprintf('*')
*         end
  fprintf('\n') 
end

I dont think there is. My for loop does what your repmat does. So far i could reduce my code by using your style of index increment then decrement as so:

before: for i= 1:ceil(row/2);
and:    for j=ceil(row/2)-1:-1:1
-------------------------
after:  for i= [1:(row+1)/2,(row-1)/2:-1:1]

This reduction leads to my code being 2 lines longer than your code. You win this time... Lol.

Also, it seems like your code could be reduced to a super short:

 numRows = 3     % input('enter something');
    matSpaceStar=[[1:2:numRows,numRows-2:-2:1];[numRows-[1:2:numRows,numRows-2:-2:1]]/2];
for ii = matSpaceStar
    fprintf([repmat(' ',1,ii(2)),repmat('*',1,ii(1)),'\n']);
 end

Earlier, were you hinting that there is a shorter way to make the shape than using a for loop?

If you could spare more time, could you tell me?

I thought about it, but have run out of time and need to get back to homework. This problem is pretty fun.

Thank you for your help!