C plus plus program for finding practical numbers?

Answer 1

#include<iostream>

#include<vector>

#include<algorithm>

#include<cassert>

template<typename _Ty>

class subset

{

public:

using value_type = typename _Ty::const_iterator;

using subset_type = std::vector<value_type>;

using iterator = typename subset_type::iterator;

using const_iterator = typename subset_type::const_iterator;

using reverse_iterator = typename subset_type::reverse_iterator;

using const_reverse_iterator = typename subset_type::const_reverse_iterator;

using size_type = typename subset_type::size_type;

inline explicit subset (const _Ty& set);

subset (const subset& source) = delete;

subset (subset&& source) = delete;

subset& operator= (const subset& source) = delete;

subset& operator= (subset&& source) = delete;

const subset_type& first (size_type size);

const subset_type& next (void);

private:

size_type m_size;

subset_type m_set;

subset_type m_subset;

const_iterator find (const value_type& value) const;

};

template<typename _Ty>

subset<_Ty>::subset (const _Ty& set): m_size (set.size()), m_set (), m_subset ()

{

for (value_type it=set.begin(); it!=set.end(); ++it)

m_set.push_back (it);

}

template<typename _Ty>

typename subset<_Ty>::const_iterator subset<_Ty>::find (const value_type& value) const

{

const_iterator it=m_set.begin();

while (it!=m_set.end() && *it!=value) ++it;

return it;

}

template<typename _Ty>

const typename subset<_Ty>::subset_type& subset<_Ty>::first (size_type count)

{

assert (0U < count);

assert (count <= m_set.size());

m_size = count;

m_subset.clear();

for (const_iterator it=m_set.begin(); count--; ++it)

m_subset.push_back (*it);

assert (m_subset.size() k)

found = true;

}

}

if (!found)

return false;

}

return true;

}

int main()

{

for (size_t n=1; n<=100; ++n)

if (is_practical (n))

std::cout << n << ", ";

std::cout << "\b\b " << std::endl;

}

Output:

1, 2, 4, 6, 8, 12, 16, 18, 20, 24, 28, 30, 32, 36, 40, 42, 48, 54, 56, 60, 64, 66, 72, 78, 80, 84, 88, 90, 96, 100