note
chipmunk
Like I said before, figuring out when to use parens is the tricky part. :) MeowChow pointed out that my solution didn't account for operators which aren't associative ("2 3 4 + -" should be "2 - (3 + 4)" instead of "2 - 3 + 4"). Then I noted that this information was missing from the data provided in the original problem.
<p>
I decided to tackle the problem of associativity, and came up with this solution, at 171 characters in the body of the sub:
<code>%o = ('+' => 1,
'-' => 1,
'*' => 2,
'/' => 2,
);
%a = ('-' => 1,
'/' => 1,
);
sub rpn2ltr {
for$i(@r=@_){if($p=$o{$i}){$r=$p>($r=pop)->[0]||($p==$r->
[0]&&$a{$i})?"($r->[1])":$r->[1];$l=$p>($l=pop)->[0]?"($l->[
1])":$l->[1]}push@_,[$p||9,$p?"$l $i $r":$i]}$_[-1][1]
}
</code>
It's pretty ugly. :/ I hope someone will provide a more elegant solution!
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