DDraceNetwork - developer

god damn it. today was very possible to get in the top100

ddnet-maps

[ddnet-maps:master] 1 new commit

6acc342 M Gedan2 - ddnet-maps

flex

i dont get the second part

09:21

the meaning

09:21

09:22

ahhh

09:25

done

09:26

https://github.com/edg-l/adventofcode-2020/blob/master/day5.rs

09:26

i think i got a pretty solution

09:31

09:31

Ryozuki

i dont get the second part

I did just sum from lowest to highest - sum all given ids

read full msgs bro

10:36

i already did it

Yeah but you iterate and sort, pah :d

@Ryozuki I chose nim and abused binary search

https://github.com/def-/adventofcode-2020/blob/master/day5.nim

Is set a hash set in nim?

13:44

I just replaced F and B with 0 and 1 respectively to get binary and than used a standard lib function to convert to a number

@timakro yes, but I didn't use the regular hash sets (https://nim-lang.org/docs/sets.html) but instead the more efficient bit sets: https://nim-lang.org/docs/system.html#system-module-sets

14:39

thus also limited to int16

on codewars there was "count number of vowels a-e-i-o-u in string" and I was able to remove all branches happy

int getCount(const std::string& inputStr){
  int num_vowels = 0;
  for (auto i : inputStr){
    num_vowels += (0x208222 >> (i & 0x9F)) & 0x1;
  }
  return num_vowels;
}

nice

thanks

@ReD looks like undefined behavior. did you mean (0x208222 >> (i & 0x1f)) & 0x1?

15:57

(which probably also represents what your code will compile to)

16:00

indeed, they compile to the same assembly: https://godbolt.org/z/865Kez

Compiler Explorer - C++ (x86-64 gcc 10.2)

int getCount(const std::string& inputStr){ int num_vowels = 0; for (auto i : inputStr){ num_vowels += (0x208222 >> (i & 0x9F)) & 0x1; } return num_vowels; } int getCount2(const std::string& inputStr){ int num_vowels = 0; for (auto i : inputStr){ num_vowels += (0x208222 >> (i & 0x1F)) & 0x1; } return num_vowels; }

16:02

these are the characters you count:

>>> "".join([chr(i) for i in range(128) if (0x208222 >> (i & 0x1F)) & 0x1])
'\x01\x05\t\x0f\x15!%)/5AEIOUaeiou'

(edited)

the inputStr only contains lower case numbers and space, so I only considered that range

lowercase letters? ah okay

if it was whole range I would need to think about something else

nice optimization then

thanks I will think about the "all characters challenge"

How did you find the 2 constants (0x208222, 0x9F)?

curious aswell

16:46

some math stuff?

16:46

xD

binary I think

ok let's explain :D we start with character i &ing 0x9F is just subtracting 96 because 0x9f = 1001'1111, and &ing this removes the 64 and 32 bit (which adds to 96) it's useful because 'a' == 97, so it's just one off 0x208222 is 1000001000001000100010 in binary which has 5 binary digits at positions : 1, 5, 9, 14 and 21 this corresponds to the position of vowels after 96 :

'a' = 97 + 0        == 96 + 1
'e' = 97 + 4        == 96 + 5
'i' = 97 + 8        == 96 + 9
'o' = 97 + 14       == 96 + 14
'u' = 97 + 20       == 96 + 21

so if after rightshifting 0x208222 by (i - 96) the last bit is 1 ,it must be a vowel (edited)

ohh

16:47

nice

@heinrich5991 and 0x9F and 0x1F compile into the same binaries because if a character was greater than 128 (96 + 32) than 0x208222 >> 32 results in 0, which has no 1 at the last bit . it doesn't matter for this string range, but this could lead to undefined behavior (ISO 9899:2011 6.5.7 Bitwise shift operators) which is avoidable, so you are correct that I should use 0x1F instead of 0x9F

(edited)

just had this happen to two ppl on korean ddnet server. dk why

@nils send me their map and savecode (or name) in DM

Zwelf

[ddnet/ddnet] Issue reopened: #3380 AddressSanitizer: heap-buffer-overflow in CSaveTee::GetString(CSaveTeam const*) /home/teeworlds/src/master/src/game/server/save.cpp:226:2

i have one question

go ahead

how the f u guzs are hosting server

23:10

servers*

we rent a vps and run our servers on them

ough