http://qs1969.pair.com?node_id=79834

in reply to (Golf) Shortest Graph Distance

Here's a solution, which I'm fairly certain works as intended (but we saw where that got me last time ;)
sub path { (*g,\$f,\$t)=@_;@s=map[\$f,\$_,\$r{\$_}],keys%{*r=\$g{\$f}}; push@s,map[@p,\$_,\$d+\$r{\$_}],keys%{*r=\$g{\$n}} while(@s=sort{\$b->[-1]<=>\$a->[-1]}@s),\$d=pop@{*p=pop@s}, (\$n=\$p[-1])ne\$t;@p }
170 characters... Yikes! I'm sure someone can do better than that!

Update: Hey, I don't need to do that complicated initialization of @s!

sub path { (*g,\$f,\$t)=@_;@s=[\$f,0]; push@s,map[@p,\$_,\$d+\$r{\$_}],keys%{*r=\$g{\$n}} while(@s=sort{\$b->[-1]<=>\$a->[-1]}@s),\$d=pop@{*p=pop@s}, (\$n=\$p[-1])ne\$t;@p }
142 characters!

Update:

This solution will be very slow on the NYC to SF test case, because it gets stuck moving back and forth between Chicago, Cleveland, and Detroit for a while, because SF is so far away. However, it will find the solution eventually.

Of course, this could be fixed by preventing the code from moving back to a node that has already been visited, but we're optimizing for character count, not for speed of execution! ;)