This is the answer of Exercise #9: No for-loops.

Question

Replace the for-loop. You will need:


int ProductNonZeroPositives(const std::vector<int>& v)

{

  const size_t sz = v.size();

  int product = 0;

  for (size_t i=0; i!=sz; ++i)

  {

    if (v[i]>0) product*=v[i];

  }

  return product;

}

Answer


//From http://www.richelbilderbeek.nl/CppAccumulate_if.htm

template

  <

  typename InputIterator,

  typename ElementType,

  typename BinaryOperation,

  typename Predicate

  >

const ElementType std::accumulate_if(

  InputIterator first,

  const InputIterator last,

  ElementType init,

  const BinaryOperation binary_op,

  const Predicate predicate)

{

  for (; first != last; ++first)

    if (predicate(*first)) init = binary_op(init, *first);

  return init;

}



#include <vector>



//From http://www.richelbilderbeek.nl/CppProductNonZeroPositives.htm

int ProductNonZeroPositives(const std::vector<int>& v)

{

  return ::std::accumulate_if(

    v.begin(),

    v.end(),

    1,

    std::multiplies<int>(),

    std::bind2nd(std::greater<int>(),0));

}

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(C++) Answer of exercise #9: No for-loops #19

Question

Answer