## Search found 546 matches

Sun Feb 01, 2015 4:48 pm
Forum: Programming languages
Topic: [C++] GMP hamming weight
Replies: 3
Views: 8456

### Re: [C++] GMP hamming weight

For fixed length integers (e.g. 32 bit ints) there is a well known clever way to do this: int countBits(unsigned x) { x = x - ((x >> 1) & 0x55555555); x = (x & 0x33333333) + ((x >> 2) & 0x33333333); x = (x + (x >> 4)) & 0x0F0F0F0F; x = x + (x >> 8); x = x + (x >> 16); return x & 0x0000003F; } Howeve...
Wed Jan 14, 2015 8:36 am
Forum: News, Suggestions, and FAQ
Topic: Errors/Warnings/Bugs
Replies: 579
Views: 180232

### Re: Problem 8 is blank?

This also breaks the "View the details of all problems on one page" option. It shows nothing beyond problem 7.
Tue Jan 13, 2015 11:44 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 497
Replies: 5
Views: 2721

### Re: Problem 497

Thanks, hk.
Tue Jan 13, 2015 2:40 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 497
Replies: 5
Views: 2721

### Problem 497

In 497 it says: Let E(n,k,a,b,c) be the expected minimal number of squares that Bob travels during a single optimally-played game. I don't understand what "minimal" means here. What is being minimised? It already says it is for the optimal game. To me, minimal would be when the randomly chosen direc...
Sat Jan 03, 2015 4:16 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 182
Replies: 10
Views: 4167

### Re: Problem 182

leghorn wrote:The numbers are p=1009 and q=3643. Since phi is (p-1)(q-1), shouldn't the last line read phi(1008, 3642)?
No, it is written as if phi is a function of p and q, so as phi(p,q). So it is either (p-1)(q-1) or phi(p,q), which are equal by definition, but not some bizarre mix of the two.
Wed Dec 31, 2014 9:19 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 030
Replies: 5
Views: 2676

### Re: Problem 030

Wow this is so stupid. Clearly 10 is a sum of its digits to the fourth power. No, it isn't the sum of its digits to the fourth power. 1^4+0^4 is not equal to 10. And the reasoning "As 1 = 1^4 is not a sum it is not included." is SO stupid! As 6^4 is not a sum it should not included as well, but it ...
Wed Dec 31, 2014 9:15 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 027
Replies: 25
Views: 9791

### Re: Problem 027

aware wrote:are a and b necessarily integers? Or can they be rational/irrational?
What does the polynomial evaluate to for n=0 and n=1?
Mon Dec 22, 2014 10:04 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 494
Replies: 10
Views: 4069

### Re: Problem 494

Not asking for hints or clues, but would kindly request an explanation on the meaning of this wording: Let Sm be the set of all sequence prefixes of length m. Two sequences {a1, a2, ..., am} and {b1, b2, ..., bm} in Sm are said to belong to the same prefix family if ai < aj if and only if bi < bj f...
Tue Dec 16, 2014 11:21 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 234
Replies: 4
Views: 2170

### Re: Problem 234

That's the correct sum.
Tue Dec 16, 2014 10:49 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 234
Replies: 4
Views: 2170

### Re: Problem 234

54 should not be on your list, but 55 should.
Mon Dec 15, 2014 7:05 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 407
Replies: 9
Views: 4834

### Re: Problem 407

All of that is correct.
Sat Nov 29, 2014 12:34 am
Forum: News, Suggestions, and FAQ
Topic: New awards.
Replies: 68
Views: 31314

### Re: New awards.

(Sorry if this is in the wrong place) Could someone confirm how Decimation II works? I read it to mean one problem from each of 20X, 21X, 22X...29X, so at least 10 problems with one from each decade between 200->300. I've completed it to my understanding but it's not shown up. Thanks The way I read...
Mon Nov 03, 2014 10:49 pm
Forum: Clarifications on Project Euler Problems
Topic: Problem 487
Replies: 5
Views: 3079

### Re: Problem 487

You can interpret the question as follows: Define T k (n,p) as S k (n) mod p. The problem then asks for [sum]T k (n,p) Albert's point is that this is mathematically sloppy. The integers mod p form a field, Z p = Z/pZ for any prime p. It is not possible to add an element of say Z 5 to an element of ...
Wed Oct 29, 2014 11:02 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 431
Replies: 10
Views: 4587

### Re: Problem 431

Hi, I don't understand why 1.114785284 has 3 squared decimal places ... At first sight, I see "1" twice and "4" twice too, giving thus 4 places... So this is not about single digits being squares... Can someone please explain me the decision criterion ? Many thanks for your help ! It simply has 9 d...
Thu Oct 23, 2014 9:09 am
Forum: Recreational
Topic: Cryptographic system puzzle
Replies: 0
Views: 2756

### Re: Cryptographic system puzzle

Here is a 14x14 board for k=2. A...D...G...J. BC..EF..HI..K. .A...D...G...J .BC..EF..HI..K .............. .............. L...O...R...U. MN..PQ..ST..V. .L...O...R...U .MN..PQ..ST..V .............. .............. WXY....Z12.... ..WXY....Z12.. For larger k you can similarly build boards by putting toge...
Wed Oct 22, 2014 10:07 am
Forum: Recreational
Topic: The Tetris Problem
Replies: 6
Views: 4811

### Re: The Tetris Problem

Here are a few simpler solutions for width 4, where the straight piece (not shown) is slotted in last. Unlike the solution in my previous post, these never have any unconnected floating squares when rows disappear. TTT. LTSS LSS. LLOO ZZOO JZZ. JJJ. ----- OOS. OOSS LLLS LTTT ZZT. JZZ. JJJ. ----- LLL...
Tue Oct 21, 2014 4:55 pm
Forum: Recreational
Topic: The Tetris Problem
Replies: 6
Views: 4811

### Re: The Tetris Problem

Here is a solution for the width 4 problem.

Code: Select all

S...
SSOO
.SOO

S...
.SOO

...L
SLLL
.SOO

...L
.SOO

.J.Z
.JZZ
JJZL
.SOO

.J.Z
.JZZ
.SOO

ITTT
IJTZ
IJZZ
ISOO
I wrote a little computer program for it, as I was not able to get anything by hand. This is the first solution it produced.
Sat Oct 18, 2014 9:28 pm
Forum: Recreational
Topic: The Tetris Problem
Replies: 6
Views: 4811

### Re: The Tetris Problem

Code: Select all

L......
LIIIIOO
LL...OO

.......
L......
LL...OO

TTTZJJJ
LTZZSSJ
LLZSSOO
The 7 rows of width 4 seems trickier, and I have not yet found a solution.
Wed Sep 17, 2014 8:48 am
Forum: Combinatorics
Topic: Combinatorial problem
Replies: 1
Views: 7177

### Re: Combinatorial problem

lopez25 wrote:You can not build the 5-uple 1-2-3-4-5 if at least one of the triplet 1-2-3 or 1-2-4 is missing.
I don't understand how you are building the 5-tuples.
If you are just taking the union of some triplets, then for example {1,4,5} and {2,3,4} build {1,2,3,4,5} without using either {1,2,3} or {1,2,4}.
Thu Aug 21, 2014 9:46 am
Forum: Clarifications on Project Euler Problems
Topic: Problem 058
Replies: 32
Views: 12006

### Re: Problem 058

If you think everything's working correctly and you've run out of prime numbers, what course of action do you think this suggests? Generate more primes ? :D I'am sorry but I have been stuck on this problem for 3 days generating up to 707081281 sieve matrix and still hitting ~10% ratio The code take...