multimap, avoiding duplicated key->value pairs

[He Shiming]

Hi Folks,

Happy holidays! I have a question regarding STL multimap. Basically, the
current multimap<int,in t> look like this:

key=>value
1=>10,
1=>20,
1=>30,

When I'm inserting new key value pairs, I need to ensure that those pairs
already in the multimap can't be inserted again. Say that 1=>40 is okay, but
1=>10 is not okay. So that I get unique key->value pairs in the multimap.

I know that upon each insertion, I can do a check by iterating through keys
and values. But is there any easier or hopefully faster way to do this?

Thanks in advance,
--
He Shiming

[Donovan Hawkins]

"He Shiming" <mailbill(NOSPA M)@21cn.com.nos pam> wrote in message
news:33******** *****@individua l.net...

Happy holidays! I have a question regarding STL multimap. Basically, the
current multimap<int,in t> look like this:

key=>value
1=>10,
1=>20,
1=>30,

When I'm inserting new key value pairs, I need to ensure that those pairs
already in the multimap can't be inserted again. Say that 1=>40 is okay, but 1=>10 is not okay. So that I get unique key->value pairs in the multimap.

How about using a map< int, set<int> > instead?

std::map< int, std::set<int> > m;
m[1].insert(10);
m[1].insert(20);
m[1].insert(30);
m[1].insert(40);
m[1].insert(10);
assert( m[1].size() == 4 );

Donovan Hawkins

[He Shiming]

Hi Donovan,

Thank you for your answer. As I'm trying to use set<> on std::wstring (not
"int" in my actual case), I get a lot of error messages when compiling, like
this:

e:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\includ e\utility(41) :
error C2664: 'std::set<_Kty> ::set(const std::set<_Kty>: :key_compare &)' :
cannot convert parameter 1 from 'const std::allocator< _Ty>::value_typ e' to
'const std::set<_Kty>: :key_compare &'
with
[
_Kty=std::wstri ng
]
and
[
_Ty=std::wstrin g
]
and
[
_Kty=std::wstri ng
]
Reason: cannot convert from 'const std::allocator< _Ty>::value_typ e'
to 'const std::set<_Kty>: :key_compare'
with
[
_Ty=std::wstrin g
]
and
[
_Kty=std::wstri ng
]
No constructor could take the source type, or constructor overload
resolution was ambiguous
f:\-= Projects =-\-= Programming
=-\MediaMan\Media Man\Framework\S ystem\RegKeyEx. h(93) : see reference to
function template instantiation
'std::pair<_Ty1 ,_Ty2>::pair<st d::wstring,std: :allocator<_Ty> ::value_type>(c onst
std::pair<std:: wstring,std::al locator<_Ty>::v alue_type> &)' being compiled
with
[
_Ty1=const std::wstring,
_Ty2=std::set<s td::wstring>,
_Ty=std::wstrin g
]

I'm wondering, as I'm not familiar with std::set, can it be used with
std::wstring, std::string or other objects?

Thanks,
--
He Shiming

"Donovan Hawkins" <ha*****@uci.ed u> wrote in message
news:it******** **********@twis ter.socal.rr.co m...

"He Shiming" <mailbill(NOSPA M)@21cn.com.nos pam> wrote in message
news:33******** *****@individua l.net...

Happy holidays! I have a question regarding STL multimap. Basically, the
current multimap<int,in t> look like this:

key=>value
1=>10,
1=>20,
1=>30,

When I'm inserting new key value pairs, I need to ensure that those pairs
already in the multimap can't be inserted again. Say that 1=>40 is okay,

but

1=>10 is not okay. So that I get unique key->value pairs in the multimap.

How about using a map< int, set<int> > instead?

std::map< int, std::set<int> > m;
m[1].insert(10);
m[1].insert(20);
m[1].insert(30);
m[1].insert(40);
m[1].insert(10);
assert( m[1].size() == 4 );

Donovan Hawkins

[He Shiming]

I'm sorry I got mixed up. I've worked it out now. Thank you very much for
your help.

--
He Shiming

"Donovan Hawkins" <ha*****@uci.ed u> wrote in message
news:it******** **********@twis ter.socal.rr.co m...

"He Shiming" <mailbill(NOSPA M)@21cn.com.nos pam> wrote in message
news:33******** *****@individua l.net...

Happy holidays! I have a question regarding STL multimap. Basically, the
current multimap<int,in t> look like this:

key=>value
1=>10,
1=>20,
1=>30,

When I'm inserting new key value pairs, I need to ensure that those pairs
already in the multimap can't be inserted again. Say that 1=>40 is okay,

but

1=>10 is not okay. So that I get unique key->value pairs in the multimap.

How about using a map< int, set<int> > instead?

std::map< int, std::set<int> > m;
m[1].insert(10);
m[1].insert(20);
m[1].insert(30);
m[1].insert(40);
m[1].insert(10);
assert( m[1].size() == 4 );

Donovan Hawkins