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Try it yourself
Posted: Thu Mar 06, 2014 8:34 pm
by zprogrammer
Technical puzzle
Below code in REXX generates prime numbers present between 1 to 1000.
Try to solve the same puzzle in Cobol.If you are able to solve in Cobol try a different language.
See how many languages you could solve the below problem
Code: Select all
/*REXX*/
DO Y = 1000 TO 1 BY -1
N = 0
DO X = 1 TO 1000 BY +1
Z = INDEX(Y/X,'.')
IF Z = 0 THEN DO
N = N+1
Y = RIGHT(Y,4)
END
END
IF N<=2 THEN DO
SAY Y 'IS A PRIME NUMBER'
END
END
Re: Try it yourself
Posted: Thu Mar 06, 2014 9:28 pm
by enrico-sorichetti
programming note...
the INDEX builtin is not portable
use pos reversing the operands
why use pos when You have available the modulus operation //
and why ... why ... why ...
I tested Your algorithm for 10000 number
and the elapsed was 1 minute and 23 seconds
here is a better solution :ugeek:
Code: Select all
primes = "3 5 7 11 13 17 19"
do n = 21 to 10000 by 2
if right(n,1) = "5" then ,
iterate n
do p = 1 to words(primes)
if n//word(primes,p) = 0 then ,
iterate n
end
primes = primes n
end
say " 1"
say " 2"
do p = 1 to words(primes)
say right(word(primes,p), 5)
end
the elapsed for above algorithm is 2.61 seconds
skipping the division by 5 provides just a very small gain U up to 10000
2.61 instead of 2.66
Re: Try it yourself
Posted: Thu Mar 06, 2014 10:01 pm
by zprogrammer
Got to break my fingers before posting next time
Re: Try it yourself
Posted: Fri Mar 07, 2014 1:26 am
by enrico-sorichetti
for interesting problems I suggest to lurk here
https://projecteuler.net/problems
if I just could remember my login I could pull out my solutions
I wrote them in REXX, python, C
IIRC I solved about 100 problems, too bad that also the backup of my coding has gone
