An interesting problem

[McGlinchy, Alistair]

03 January 2007 19:33 Andy Armstrong:
> On 3 Jan 2007, at 14:03, Paul Orrock wrote:
> > Does anyone have any clever ways of doing this other than brute
> > forcing it by checking every possible range (in a 100 by 30 
> table).  
> > And if brute forcing it is the only option (which I suspect it is)  
> > does anyone have any clever ways of doing it. Using numbers for  
> > columns and rows instead of letters is fine.
> 
> If you do end up brute forcing it you may be able to speed it up by  
> first computing a quad tree. To do that you'd calculate the sum of  
> each 2x2 meta-square and then do that recursively until you end up  
> with a single square that's the sum of all the squares like this:
> 
That's sort of what I have been playing with, but it still doesn't seem
impressively fast. There's a large number of off-by-one errors possible
in here, but the answers seems to tally up when I check in Excel. 

I'd be interested in comments:

Cheers

Alistair









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