Re: longuest interleaved sequences

[Jaroslav Hajek]

On Thu, May 20, 2010 at 10:19 PM, Judd Storrs <address@hidden> wrote:
> On Thu, May 20, 2010 at 3:39 PM, Jaroslav Hajek <address@hidden> wrote:
>> what about
>>
>>  x = sort(rand(50,1)) ;
>>  y = sort(rand(54,1)) ;
>>
>> [~, ix] = unique (lookup (y, x));
>> x = x(ix);
>> [~, iy] = unique (lookup (x, y));
>> y = y(iy);
>>
>> and remove one element from the longer sequence if needed.
>
> I think this generates an interleaved subset of x and y that is
> longest. It tosses values out, though. I was trying to find the
> longest continuous subsequence. Your code finds the longest (possibly
> non-continuous) subsequence which may be what Pascal was wanting.

Well, subsequence != contiguous subsequence. At least I think
contiguity was not specified.

>I always forget about lookup() ;)
>

That's not that bad, you may be aware of the other funcs (histc and
ismember) that use lookup behind the scene. But they generally do some
extra work, while lookup is a "raw" binary search.

-- 
RNDr. Jaroslav Hajek, PhD
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz