How to insert a pair using multiset in C++

Question

I want to insert an integer value and a pair in a multiset.

So I declared it as:

multiset < int, pair < int, int> > mp;
int m,n,p;

To insert in multiset I tried this :

mp.insert(make_pair(m, make_pair(n,p))); // Compile time error

But its giving compile time error... Could someone please suggest the correct method to implement it.

Are you sure you don't want a [`multimap`](http://en.cppreference.com/w/cpp/container/multimap)? — ildjarn, Oct 04 '12 at 19:33
They can in `multimap` too – hence the separate types `map` and `multimap`. ;-] — ildjarn, Oct 04 '12 at 19:44

score 7 · Accepted Answer · answered Oct 04 '12 at 19:30

7

The type multiset<int,pair<int,int>> is trying to create a multiset where the Key is int and the Compare is pair<int,int>. This is nonsensical. You either want to use

multiset<pair<int,pair<int,int>>>

or you want to use

multiset<tuple<int,int,int>>

The former type (pair<int,pair<int,int>>) matches the expression you're using to insert into the set (make_pair(m, make_pair(n,p))). If you use the latter, you'll want make_tuple(m,n,p).

answered Oct 04 '12 at 19:30

Lily Ballard

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thanks for the answer,somehow it was working for multimap but fails in case of multiset, could you please suggest some possible reasons ? – Rishabh Oct 04 '12 at 19:38
2

@rishabh : `multimap` has a key and a value, `multiset` only has a key. What are you trying to accomplish? It's hard to help when you show nonsense code and don't explain the goal. ;-] – ildjarn Oct 04 '12 at 19:44
@ildjarn thanks for the clarification,i am new to these concepts so I should better study them in greater detail before asking any further question... – Rishabh Oct 04 '12 at 19:49

How to insert a pair using multiset in C++

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