From: Robert Klemme <shortcutter@...>
Date: 2008-05-05T15:25:04+09:00
Subject: Re: Array combination check

On 04.05.2008 14:50, Nadim Kobeissi wrote:
> Xavier Noria wrote:
>> What is a combination?
> 
> Please allow me to make myself more clear:
> bunny=["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
> cow="hello"
> 
> I want to test all possible combinations of the items inside bunny (the 
> alphabet) starting from the smallest to the biggest (a, then b, then c.. 
> then aa, then ab, then ac, etc.) until I arrive to a case in which the 
> combination == cow, which means the combination would be "hello".

I am sorry, but this seems a rather silly approach.  All you get as 
output is the information whether /cow/ can be built using characters in 
/bunny/.  Your approach has at least O(n*n) while it seems there is a 
much simpler and faster (with O(n)) algorithm available:

irb(main):001:0> require 'set'
=> true
irb(main):002:0> bunny=("a".."z").to_set
=> #<Set: {"v", "k", "w", "l", "a", "x", "m", "b", "y", "n", "c", "z", 
"o", "d", "p", "e", "q", "f", "r", "g", "s", "h", "t", "i",
u", "j"}>
irb(main):003:0> cow="hello"
=> "hello"
irb(main):004:0> def t(s,chars)
irb(main):005:1> s.scan(/./) {|m| return false unless chars.include? m}
irb(main):006:1> true
irb(main):007:1> end
=> nil
irb(main):008:0> t cow, bunny
=> true
irb(main):009:0> t "___", bunny
=> false
irb(main):010:0>

Kind regards

	robert