How to swap the two consecutive bits of unsigned integer ?

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posted Nov 4, 2013 by Anuj Yadav

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swap is needed only if nth and nth bit are different ie 01 or 10.

commented Nov 5, 2013 by Salil Agrawal

int main()
{
  unsigned int N,Mask1,Mask2,Mask3,T1,T2,T3,k;
  scanf("%u",&N);
  scanf("%u",&k);
  /* 1's in bit 0 and bit 1 position */
  Mask1=0x0003;
  /* 1's in positions k and k+1 and 0's else where */
  Mask2=Mask1<<k;
  /* 0's in positions k and k+1 and 1's else where */
  Mask3=~Mask2;
  /* bring bits at position k and k+1 to bit 0 and bit 1 position*/
  T1=(N&Mask2)>>k;
  if(T1!=0&&T1!=3)
  {
    T1=T1^Mask1; /* swap */
    T1=T1<<k; /* shift the swapped bits to original position*/
    T2=N&Mask3;
    /* append other bits(0 to k-1 and k+2 to 15) */
    T3=T2|T1;
    printf("%u",T3);
  }
  else
    printf("%u",N);
}

commented Nov 6, 2013 by anonymous

unsigned char t1,t2;
t1=c&0*0F;
t2=c&0*F0;
t1=t1<<4;
t2=t2>>4;
return (t2|t1);

commented Nov 7, 2013 by anonymous

1 Answer

Try this to swap all consecutive bits

For 8 bit integer

u_int8 swap_bits(u_int8 ch)
{
    return ((ch & 0xAA)>>;1 ) | ( (ch & 0x55) << 1);
}

For 16 bit integer

u_int16 swap_bits(u_int16 ch)
{
    return ((ch & 0xAAAA)>>;1 ) | ( (ch & 0x5555) << 1);
}

answer Nov 5, 2013 by anonymous

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How to swap the two consecutive bits of unsigned integer ?

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