From: mrchameleon@... (Chris Reay)
Date: 2002-09-19T10:18:17+09:00
Subject: Re: How to Efficiently Calculate the Pattern of Zeros and Ones?

William Djaja Tjokroaminata <billtj@z.glue.umd.edu> wrote in message news:<amagpp$lkf$1@grapevine.wam.umd.edu>...
> Hi,
> 
> I am dealing with this algorithmic problem.  I have an array of arbitrary
> integers.  I have to count the occurences of 1's with the pattern
> 
>     "0 0 ... 0 1 0 .. 0 0"
> 
> in the array.  The minimum number of zeros on each side of the 1 is a
> parameter, say m = 2.  Also at the beginning and at the end of the array,
> the boundary condition does not require the minimum number of zeros, as
> long as they are zeros (or non-existent).
> 
> For example, with m = 2:
> 
>     [1 0 0 1 0 0 5 1]   --> 2
>     [0 0 1 0 0 1 0 2]   --> 1
>     [1 0 1 0 1 0 1 0]   --> 0
>     [1 0 0 0 0 0 1 0]   --> 2
> 
> Typical array length will be around 24.  The problem is I will have
> thousands, if not hundreds of thousands, of such arrays.  What is a good
> way to do it in Ruby?  (Even coverting the array first to, for example,
> string and then use regexp, is also fine as long as it is efficient.)
> 
> Regards,
> 
> Bill

Is this too slow?

arr.select { |i| i ==1 }.size

Yours

Chris