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  1. #include <stdio.h>
  2.  
  3. unsigned int bits0(unsigned int num) {
  4. 	int count = 0; while(num) num >>=1, ++count; return count;	
  5. }
  6. unsigned int bits1(unsigned int x) {
  7.    int y, m=0, n=0;
  8.  
  9.    y = x - 0x100;       
  10.    m = (y >> 16) & 8;
  11.    n = n + m;
  12.    x = x << m;
  13.  
  14.    y = x - 0x1000;      
  15.    m = (y >> 16) & 4;
  16.    n = n + m;
  17.    x = x << m;
  18.  
  19.    y = x - 0x4000;      
  20.    m = (y >> 16) & 2;
  21.    n = n + m;
  22.    x = x << m;
  23.  
  24.    y = x >> 14;         
  25.    m = y & ~(y >> 1);
  26.    return 14 - n + m;
  27. }
  28. int main(int argc, char **argv) {
  29. 	unsigned int j=1<<12,i=0;
  30. 	for (;i<10;++i,j<<=1){
  31. 	  unsigned int d = j|1;
  32. 	  printf("%lu==%lu\n", bits0(d), bits1(d));
  33. 	}
  34. 	for (i=1;i<65536;++i)
  35. 		if(bits0(i)!=bits1(i))
  36. 	  		printf("ERROR i=%d %lu!=%lu\n", bits0(i), bits1(i));
  37.  
  38.   return 0;
  39. }
Success #stdin #stdout 0s 2292KB
comments (?)
stdin
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Standard input is empty
stdout
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13==13
14==14
15==15
16==16
17==18
18==22
19==76
20==2056
21==1
22==1
https://ideone.com/scwkXl
language:
C (gcc 8.3)
created:
12 years ago
visibility:
secret

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