Square spiral
First read the problem description.
Since we want to draw the spiral using ascii characters we need to
draw it in one pass. Now imagin a grid n*n, for each cell
(x,y) in the grid we need to decide wheter to fill the
cell, or to leave it blank. To do so we simply find the coordinates
(cornerx,cornery) of each corner along a diagonal and the
length of each side that springs from that corner and see if
our coordinates (x,y) are contained in that side.
Here is a sample output (the output may appear distorted if you don’t use monospace font):
@@@@@@@@@@@@@@@@
@
@@@@@@@@@@@@@ @
@ @ @
@ @@@@@@@@@ @ @
@ @ @ @ @
@ @ @@@@@ @ @ @
@ @ @ @ @ @ @
@ @ @ @ @ @ @ @
@ @ @ @@@ @ @ @
@ @ @ @ @ @
@ @ @@@@@@@ @ @
@ @ @ @
@ @@@@@@@@@@@ @
@ @
@@@@@@@@@@@@@@@Source code of the solution(s):