use strict; sub spiral { my\$S=pop;my(\$z,\$s,\$t,\$d,\$x,\$y,@b)=(\$S**2,1);@_=([1, 0],[0,1],[-1,0],[0,-1]);\$b[\$S][\$_]=\$b[\$_][\$S]=\$/for 0..\$S;map{\$b[\$y][\$x]=sprintf"%0*d",length\$z,\$_;(\$s, \$t)=@{\$_[++\$d%4]}if\$s&&\$b[\$y][\$x+\$s]||\$t&&\$b[\$y+\$t] [\$x];\$x+=\$s;\$y+=\$t}1..\$z;pop@b;print"@\$_"for@b; } for (1..10) { spiral(\$_); print "\n---\n"; } ##```## use strict; sub spiral { my \$size = pop; # get the size from the arguments my \$elements = \$size**2; # how many numbers in the square my \$dir=0; # we will go right at start my (\$dx,\$dy)=(1,0); # starting deltas (must match \$dir) my (\$x,\$y)=(0,0); # start top left my @board; # the board we will use my @delta=([1,0], # deltas for going right [0,1], # ... down [-1,0], # ... left [0,-1]); # ... up # Set up sentinal values in (x,\$size) and (\$size,y) # ie, a column on the right and a row at the bottom \$board[\$size][\$_]=\$board[\$_][\$size]="\n" for 0..\$size; # The strategy is to treat \$x,\$y as a cursor on the grid. # each square we move in the direction specified by \$dir # via the @delta table, assuming that is that the new # cell has not been filled already. if it has we turn to # the right by incrementing \$dir and finding new deltas. for (1..\$elements) { # neatly set up the value in the grid, we use the length of # the center element to determine how many digits to use per "cell" \$board[\$y][\$x] = sprintf"%0*d",length \$elements, \$_; # if we bump into something we need to turn to the right # the sentinals mean we dont have to check for anything other # than the cell being nonempty in the direction we are travelling (\$dx,\$dy)=@{\$delta[++\$dir%4]} if \$dx && \$board[\$y][\$x+\$dx] || \$dy && \$board[\$y+\$dy][\$x]; # and adjust our position according to the deltas \$x+=\$dx; \$y+=\$dy }; # we need to remove the bottom row as it is just a list of newlines pop @board; # and now we print it out, we dont need to remove the right hand # sentinals as they conveniently end the line for us. print"@\$_" for @board; } for (1..10) { spiral(\$_); print "\n---\n"; } ```