yes, I thought about this but it would be like extra step, which I wanted to
avoid.
andre <as@yahoo.com> wrote:
Hi,
anybody can advise how to get a key from the map having value only?
The other way around its easy of course, and map is supposed to be used
like
that.
But I need to find a key for a given value.
thanks
I am aware that this doesn't exactly answer your question,
but in case you find yourself doing this repeatedly and if
you're sure that there's always a one-to-one relationship
between keys and values, you might want to create a reversed
map where keys and values are swapped.
I have this in my toolbox:
// Caution! I had to copy-paste this together from several
// functions, so it might contain silly errors
template< typename T1, typename T2 >
inline void build_reverse_map(const std::map<T1,T2>& map,
std::map<T2,T1>& reverse_map)
{
typedef std::map<T1,T2> map_type;
typedef std::map<T2,T1> reverse_map_type;
typedef typename reverse_map_type::value_type reverse_value_type;
for( typename map_type::const_iterator it=map.begin(),
end=map.end(); it!=end; ++it )
{
assert(
reverse_map.insert(reverse_value_type(it->second,it->first)).second );
}
}
Use it like this:
void f()
{
std::map<int,string> my_map;
// fill 'my_map'
std::map<string,int> my_reverse_map;
build_reverse_map(my_map,my_reverse_map);
// use reverse map
}
HTH,
Schobi
--
SpamTrap@gmx.de is never read
I'm Schobi at suespammers dot org
"The sarcasm is mightier than the sword."
Eric Jarvis