Using pair as key for map

问题:

Based on a previous question, I am trying to create a map using a pair of integers as a key i.e. map<pair<int, int>, int> and I've found information on how to insert:

#include <iostream>
#include <map>

using namespace std;

int main ()
{
map<pair<int, int>, int> mymap;

mymap.insert(make_pair(make_pair(1,2), 3)); //edited
}   

but I can't seem to access the element! I've tried cout << mymap[(1,2)] << endl; but it shows an error, and I can't find information on how to access the element using the key. Am I doing something wrong?

回答1:

you need a pair as a key cout << mymap[make_pair(1,2)] << endl; What you currently have cout << mymap[(1,2)] << endl; is not the correct syntax.

回答2:

mymap[make_pair(1,2)]

or, with compiler support:

mymap[{1,2}]