Problems on these two questions

Neil Cerutti neilc at norwich.edu
Tue Nov 20 16:02:08 CET 2012


On 2012-11-19, Dennis Lee Bieber <wlfraed at ix.netcom.com> wrote:
> On Sun, 18 Nov 2012 17:52:35 -0800 (PST), su29090
> <129km09 at gmail.com> declaimed the following in
> gmane.comp.python.general:
>
>> 
>> I all of the other problems but I have issues with these:
>> 
>> 1.Given a positive integer  n , assign True to  is_prime if  n
>> has no factors other than  1 and itself. (Remember,  m is a
>> factor of  n if  m divides  n evenly.) 
>>
> 	Google: Sieve of Eratosthenes (might be mis-spelled)

The sieve is a nice simple and fast algorithm, provided there's a
bound on the highest n you need to check. It's much less simple
and less fast if n is unbounded or the bound is unknown.

Python's standard library isn't equipped with the an obvious
collection to use to implement it either.

>> 2.An  arithmetic progression is a sequence of numbers in which
>> the distance (or difference) between any two successive
>> numbers if the same. This in the sequence  1, 3, 5, 7, ... ,
>> the distance is 2 while in the sequence  6, 12, 18, 24, ... ,
>> the distance is 6. 
>> 
>>  Given the positive integer  distance and the positive integer
>>  n , associate the variable  sum with the sum of the elements
>>  of the arithmetic progression from  1 to  n with distance
>>  distance . For example, if  distance is 2 and  n is  10 ,
>>  then  sum would be associated with  26 because  1+3+5+7+9 =
>>  25 . 
>
> So, what have you tried?
>
> Consider: you have a "sum", you have a sequence of "elements"
> (based upon a spacing "distance"), and you have an upper bound
> "n"
>
> You need to generate a sequence of "elements" starting at "1",
> using "distance" as the spacing, until you exceed "n", and you
> want to produce a "sum" of all those elements...

This one's sort of a trick question, depending on your definition
of "trick". The most obvious implementation is pretty good.

In both cases a web search and a little high-density reading
provides insights and examples for the OP.

-- 
Neil Cerutti


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