Question

Hi, Can anyone please explain how to solve Ps1 ?
I'm trying to solve it since 2 weeks :S
Please help before I give up..

Answer 1

hi , sorry what is the meaning of Psl?

Answer 2

Are you watching the videos of this course ??

Answer 3

no

Answer 4

i study pure math and computer science but h donot hear about it

Answer 5

ok, so you can start watching from here:
http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-00-introduction-to-computer-science-and-programming-fall-2008/video-lectures/
and you will understand everything,, this group is for studying this course only.

Answer 6

ok ,thanks alot ahmed

Answer 7

You're Welcome!

Answer 8

Ahmed,
I think Mioto's port should help you. It helped me a lot. THe link is... http://openstudy.com/study#/updates/4f3bd06ce4b0fc0c1a0f200e
Or just look for Mioto...

Answer 9

can you tell what's the problem ? What part of the assignment don't you understand ?

Answer 10

Yes, what do you not understand?

Answer 11

Ok guys, I found that wanderboy solve the assignment, and here's his code: http://codepad.org/RhiGtGcn
and It do the job, but when I simulate it by hand I didn't understand this condition:
if divisor == num: in line 11, so can anyone help ?

Answer 12

The idea is that if you go through the while loop up until the point where divisor (i.e., the number that you are using to test for primality) == number, you don't need to check anymore (there are other effective ways to code it, just using wanderboy example); If that happens, you are sure that it's a prime and you can increase count.
Suppose you are testing 5, you try
5%2 != 0; 5%3 != 0; 5%4 != 0 but now divisor == num, i.e., it's a prime.

If there was some unclear points in my explanation, just go ahead and ask :-)

Answer 13

Thanks bmp, now I got it :)

Answer 14

http://codepad.org/vodLXMGf look at this other way to do this easily, i made comments for you to be clear...

Answer 15

actually your code is the second problem in the same assignment, not the first one, but thank you very much cause I was about to ask about this problem too, and you just did, Thanks Don :)

Answer 16

mmm, well in my code are both first and 2nd problem! check it out you will notice it! (cuz in order to do the 2nd you have to do the first)

Answer 17

You can see a bunch of solutions here:
http://curiousreef.com/class/mit-opencourseware-600-introduction/lesson/2/retricen/1/

Answer 18

Don, nice solution. So you can have lists operate on each other, and operation will be done every combination from the two lists, as seems you did in below?
for listrange in range(2, 1000):
for prime in range (2, listrange-1): #looking for prime numbers
if listrange%prime == 0:

Answer 19

ahmed i was also in trouble bro but i found a solution i will send it tomorrow a have not laptop and no internet at home now just wait .you know you can't give it up!