Print star ('*') diamond in C with nested loops?

Question

I want to be able to print a diamond like this when the user enters 5 for the diamond. But also will work for any value that is odd and greater than 0.

Answer 1

There are two things that occur here:

1. Indent changes (-1 to "mid", +1 "after")

2. Star count changes (+2 to "mid", -2 "after")

Now, this could be done with two loops (one for the top to "mid" and one "after"), but the values can also be determined with a little math. Let's explore that :-)

Here are the numbers:

        s(spaces)  x(stars) n(line number)
__X          2        1        0
_XXX         1        3        1
XXXXXX       0        5        2
_XXX         1        3        3
__X          2        1        4

Start by noting that s is symmetrical about the "mid":

• s = abs(2 - n)

And then that x is related to s (by 2 as noted in deltas above):

• x = 5 - (s * 2) = 5 - (abs(2 - n) * 2)

Hope that gives some insight!