Computer Science Canada [TYS] Summarize a list of numbers |
| Author: | wtd [ Sun Nov 22, 2009 1:56 am ] | ||||
| Post subject: | [TYS] Summarize a list of numbers | ||||
So, let's say we have a list of numbers like so:
We want to summarize this by getting a list of start and end points.
Implement this behavior recursively using a left fold. You may either implement your own left fold, or use one from a programming language's standard library. For those implementing in a language which does not support tail-call elimination, don't worry about stack overflows. However, the code should be written such that tail-call elimination would be at least possible. You may also assume the list is sorted in ascending order. |
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| Author: | Prabhakar Ragde [ Sun Nov 22, 2009 3:44 pm ] |
| Post subject: | Re: [TYS] Summarize a list of numbers |
It's more natural to use a right fold, and to produce the flat list, which you can easily bundle up into pairs afterwards. If you use a right fold, in a lazy language you can produce the list lazily, and it will work on infinite lists. --PR |
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| Author: | wtd [ Sun Nov 22, 2009 4:05 pm ] |
| Post subject: | RE:[TYS] Summarize a list of numbers |
I think you're right. That'll teach me to post when I'm tired. |
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