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#include <functional>
#include <set>
#include <string>
#include <unordered_map>
#include <map>
#include <iostream>
template < typename A, typename B >
using wrapped_pair = std::pair< std::reference_wrapper<A>, std::reference_wrapper<B> > ;
struct cmp_wrapped_pair
{
template < typename A, typename B > bool operator() ( const A& a, const B& b ) const
{
return a.first.get() < b.first.get() ||
( !( b.first.get() < a.first.get() ) && a.second.get() < b.second.get() ) ;
}
};
template < typename MAP_TYPE >
auto sorted_snapshot_of( const MAP_TYPE& map ) // auto: function return type deduction is C++14
{
using KEY = typename MAP_TYPE::key_type ;
using VALUE = typename MAP_TYPE::mapped_type ;
std::multiset< wrapped_pair< const VALUE, const KEY >, cmp_wrapped_pair > snapshot ;
for( auto& pair : map ) snapshot.emplace( pair.second, pair.first ) ;
return snapshot ;
}
int main()
{
const std::unordered_map< std::string, int > unordered_map
{
{ "zero", 0 }, { "one", 1 }, { "two", 2 }, { "three", 3 }, { "four", 4 },
{ "nihil", 0 }, { "unus", 1 }, { "duo", 2 }, { "tres", 3 }, { "quattuor", 4 },
{ "sunya", 0 }, { "eka", 1 }, { "dvi", 2 }, { "tri", 3 }, { "chatur", 4 }
};
// print a sorted (values, then keys) snapshot of the map
for( const auto& pair : sorted_snapshot_of(unordered_map) )
std::cout << pair.first.get() << " " << pair.second.get() << '\n' ;
}
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