Solve hanging lantern problem: Difference between revisions

=={{header|Ruby}}==

===Directly computing the count===

If compute the count directly:

<syntaxhighlight lang="ruby" line>Factorial = Hash.new{|h, k| h[k] = k * h[k-1] } # a memoized factorial

Factorial[0] = 1

def count_perms_with_reps(ar)

Factorial[ar.sum] / ar.inject{|prod, m| prod * Factorial[m]}

end

ar, input = [], ""

puts "Input column heights in sequence (empty line to end input):"

ar << input.to_i until (input=gets) == "\n"

puts "There are #{count_perms_with_reps(ar)} ways to take these #{ar.size} columns down."

</syntaxhighlight>

{{Out}}

<pre>Input column heights in sequence (empty line to end input):

1

2

3

4

5

6

7

8

There are 73566121315513295589120000 ways to take these 8 columns down.

</pre>