Hamming

[allytrice]

Can anyone please convert this piece of code to c++, It is written in python.

def hamming_distance(s1, s2):
    assert len(s1) == len(s2)
    return sum(ch1 != ch2 for ch1, ch2 in zip(s1, s2))

[Moschops]

This assumes 32 bit integers.

int bitcount(unsigned int u)
{
         unsigned int uCount;

         uCount = u
                  - ((u >> 1) & 033333333333)
                  - ((u >> 2) & 011111111111);
         return
           ((uCount + (uCount >> 3))
            & 030707070707) % 63;
}

unsigned int hamming_distance (unsigned int s1, unsigned int s2)
{
  return (bitcount( s1 ^ s2));
}

[Cubbi]

For counting bits, std::bitset<>::count is both simpler and faster (compiles to a single CPU instruction on x86, if the argument fits in a CPU register):

#include <bitset>
#include <climits>

unsigned int hamming_distance (unsigned int s1, unsigned int s2)
{
  return std::bitset<CHAR_BIT * sizeof s1>(s1^s2).count();
}

However, that Python code was for any sequence, e.g. two strings. Its C++ equivalent would be

#include <numeric>
#include <functional>
template<typename C>
int hamdist(const C& c1, const C& c2)
{
  return inner_product(c1.begin(), c1.end(),
                       c2.begin(), 0,
                       std::plus<int>(),
                       std::not_equal_to<typename C::value_type>() );
}