The Project Euler thread

[Reincarnate]

also, honorable mention for just being a really cool and interesting problem with an elegant solution:

http://projecteuler.net/problem=202

[axith]

Project Euler makes me feel dumb. I do appreciate the math tidbits that I'm forced to look up though. I had no clue of Euler's Totient function and many number theory ideas before messing with the problems.

[leonid]

http://projecteuler.net/problem=144

I still need to solve this one

[AutotelicBrown]

Those problems are fun. I'll try 328 later.

[stargroup100]

The latest problem, 473, looks really fun. http://projecteuler.net/problem=473

Right after reading it, I feel like finding the phidigital representation of an integer is NP complexity class. However, given the nature of these problems and the limit they ask for, I'm guessing there's some brilliant trick here.

EDIT: PFFFFT the trick was so stupidly obvious im dumb

[stargroup100]

This problem is still hard as balls though. The "obvious" algorithm doesn't really help you compute anything efficiently, at least not without some heavy-duty work put onto it.

[rushyrulz]

Problem 17

If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are
3 + 3 + 5 + 4 + 4 = 19 letters used in total.

If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many 
letters would be used?

NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 
23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of "and" when writing out 
numbers is in compliance with British usage.

this one was a recursive nightmare, almost wanted to pencil and paper it.

[stargroup100]

Originally Posted by rushyrulz

Problem 17

If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are
3 + 3 + 5 + 4 + 4 = 19 letters used in total.

If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many 
letters would be used?

NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 
23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of "and" when writing out 
numbers is in compliance with British usage.

this one was a recursive nightmare, almost wanted to pencil and paper it.

fyi a pencil and paper solution could take less than 10 min LOL

[leonid]

That was easier than I feared, but it still took me a couple hours to come up with the right code

[leonid]

PARI/GP rocks

[leonid]

I'm on fire

[stargroup100]

Originally Posted by leonid

PARI/GP rocks

that thing is fucking amazing

I put it on my phone LOL

[leonid]

Used Ruby this time

[rushyrulz]

Originally Posted by stargroup100

fyi a pencil and paper solution could take less than 10 min LOL

I'm aware, but I am not doing this because I want fast solutions, I'm doing this to strengthen my programming skills.

Just like how problem 19 (how many Sundays occurred on the first day of the month in the 20th century?) could be easily guessed by

Math.round(100*12/7) = 171

, but I wrote a program for it anyway.

[Reincarnate]

The first 100 problems are pretty simple

Try some later problems for more of a challenge

[rushyrulz]

I'm having a hoot with the first 100 for now D:

[igotrhythm]

90% of these have me saying "I wish I knew how to solve this problem period, let alone write a program to solve it."

[leonid]

Dynamic programming

[leonid]

Another DP
Ruby is slow..

[leonid]

~_~