C++ How to create a map from two other maps -
    how create map  mymap3  as:   std::map< vector<std::pair<int, int>>, int > mymap3   example:    mymap3[0] = ((1,3) , (1,5), 7 ) // 5 = 4 + 3  mymap3[1] = ( (2,1) , (2,4), 6 ) // 6 = 1 + 5   where key = (vector of pairs) extract 'mymap1',   and value = sum of pairs' values  in 'mymap2'.   i don't care pair order, (2,4) same (4,2)   std::map <int, vector<pair<int, int>> > mymap1; std::map< std::pair< int, int>, int>  mymap2;   here example:    mymap1[0] = (0, (1,3) , (1,5) ) mymap1[1] = (1, (2,1) , (2,4) )  mymap2[0] = ( (1,3) , 4 ) mymap2[1] = ( (1,5) , 3 ) mymap2[2] = ( (2,1) , 1 ) mymap2[3] = ( (4,2) , 5 )    i don't know how that, , try:       std::map <int, vector<pair<int, int>> > ::iterator it1 = mymap1.begin();     std::map<std::pair< int, int>, int> ::iterator it2 = mymap2.begin(); //  std::map< vector<pair<int, int> >, int> mymap3;     std::map< pai...