Maths and programming

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Mawane
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Maths and programming

Post by Mawane » 30 Jun 2014, 06:53

I found an interesting website that some of you maybe already know.
https://projecteuler.net/problem=36
It gives maths programming challenges and I'd be interested on you you guys solve them and explain here. I don't know much about programming, but I'm looking forward to see your solutions explained!

Code: Select all

The decimal number, 585 = 10010010012 (binary), is palindromic in both bases.

Find the sum of all numbers, less than one million, which are palindromic in base 10 and base 2.

(Please note that the palindromic number, in either base, may not include leading zeros.)
Another one, this one cannot be pasted here with format:
https://projecteuler.net/problem=225

Post your own challenges too, hoping for something I can solve lol.
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ElrondMcBong
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Re: Maths and programming

Post by ElrondMcBong » 30 Jun 2014, 07:43

I am studying Mathematics in 5th semester now and didn't know about this site :oops:

The "challanges" are rather simple, but there is lot of potential to optimize the runtime.
Maybe when i have some spare time i can solve some of them :)

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anpdad
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Re: Maths and programming

Post by anpdad » 30 Jun 2014, 08:38

Well, the point is exactly in optimizing the runk time im think. Imo it good siteik, prety usful, so if you have enough willpower to force you to solve stuff on a regular basis, it'll be helpful in polishing you're skils xDxD

I think i lasted two days (and like 40 problemiks) before i got tired and got bak to wasting time playing video gams 24/7.

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Tigro
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Re: Maths and programming

Post by Tigro » 30 Jun 2014, 08:57

to MW's problem: Trying half a million numbers with brute force doesn't take so much time... (exclude all even numbers)
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Mawane
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Re: Maths and programming

Post by Mawane » 30 Jun 2014, 14:06

yeah, but later in problems, bruteforce isnt an option unless you want to wait couple years xD anyway, thats the ez way, there should be a smarter way I guess
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anpdad
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Re: Maths and programming

Post by anpdad » 30 Jun 2014, 16:01

Bruteforcik works for most problems on that site, and if you solve the problem by any means, you can access a detailed answer (at least that's how it used to be couple years ago, dunno now) that usually describes several more and more optimized solutions. It kinda destroys all the fun and doesn't improve your skills much, so imo should always avoid bruteforce.

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Stini
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Re: Maths and programming

Post by Stini » 30 Jun 2014, 16:36

I think I've solved a bit over 100 problems from projecteuler, but the site doesn't allow logging in atm so I can't check for sure. I much prefer ICPC type of problems though, where the emphasis is on programming rather than math (check eg. http://uva.onlinejudge.org/ dunno if this is the best source for problems though).

Here's a stupid and ugly one-liner for 36

Code: Select all

print sum([x for x in xrange(1000000) if bin(x)[2::] == bin(x)[:1:-1] and str(x) == str(x)[::-1]])

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Zweq
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Re: Maths and programming

Post by Zweq » 30 Jun 2014, 17:05

Stini told me about this site couple of years ago when I was a complete beginner. For example I tried to solve the problem #1 without knowing what modulo is :D. Nowadays I have around 80 problems solved, can't say for sure because the website seems to have been hacked. I haven't solved any problems for a year or so though : -( I usually just did brute force solutions in python. I liked the process of understanding a problem and making own idiot solution for it, without caring about efficiency, and receiving the rewarding congratulations! -message. (ofc good fun also to see pro mans elegant solutions on the forums)
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Re: Maths and programming

Post by badyl » 2 Jul 2014, 11:03

Have a go on this:

(Not sure about the translation correctness)
Some numbers have the property of "power sum":
If we take n-digit long number and add the n-th powers of all digits we get that number.
For example 153 has this property: 153=1^3+5^3+3^3
There are 7 prime number which have this property. Find them.

I got it from IT University lecturer. He said it was possible in time under 1 minute on usual PC.
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