Timeline for Count the number of ones in an unsigned 16-bit integer
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| Jun 17, 2020 at 9:04 | history | edited | CommunityBot |
Commonmark migration
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| Mar 14, 2018 at 15:05 | comment | added | PrincePolka | Nice, 3 bytes shorter than n=__builtin_popcount(x); | |
| Jul 1, 2015 at 7:39 | comment | added | Level River St | @nmxprime the OP asks for unsigned int. for -7 = 11111111 11111111 11111111 11111001 on my 32 bit compiler, I get 30 for the fast algorithm, which is correct. For the naive algorithm, it iterates through -7, -7/2=-3, -3/2=-1, -1/2=0. That gives an incorrect answer. Changing x/=2 to x>>=1 may give the correct answer on some compilers, but C is undefined as to whether a 1 or a 0 is shifted into the empty bit for >> on negative numbers. Those compilers that shift a 1 in will go into an infinite loop. The workaround is to define x as an unsigned int. Then x=-7 loads (1<<32)-7=4294967289 into x. | |
| Jul 1, 2015 at 5:21 | comment | added | nmxprime |
The naive implmentation for(n=0;x;x/=2)n+=x&1; gives a result which is different from, for(n=0;x;n++)x&=x-1; for negative numbers. Try with x=-7, the results are confusing !
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| Apr 29, 2015 at 13:38 | history | edited | Level River St | CC BY-SA 3.0 |
edited body
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| Apr 29, 2015 at 3:58 | comment | added | Helios |
Correction to naive algorithm: for(n=0;x;x/=2)n+=x&1;
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| Mar 23, 2015 at 18:35 | comment | added | mbomb007 | "First published in 1960", impressive. | |
| Mar 18, 2015 at 4:39 | vote | accept | ayane_m | ||
| Mar 18, 2015 at 4:40 | |||||
| Mar 17, 2015 at 8:43 | history | edited | Level River St | CC BY-SA 3.0 |
added 136 characters in body
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| Mar 17, 2015 at 8:33 | comment | added | Level River St |
@edc65 so as it turns out, I reinvented the wheel. At least I saved 2 bytes by omitting the {}. It's such a simple task I shouldn´t be surprised someone already came up with it.
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| Mar 17, 2015 at 7:29 | comment | added | edc65 | Ref: graphics.stanford.edu/~seander/… | |
| Mar 17, 2015 at 2:35 | history | edited | Level River St | CC BY-SA 3.0 |
added 37 characters in body
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| Mar 17, 2015 at 2:16 | history | answered | Level River St | CC BY-SA 3.0 |