C + + several code optimization records __c++

The following is based on debug debug mode,

Map<int, string> MSS;
 clock_t C1, C2;
 C1 = Clock ();
 for (int i=0; i<500000; i++)
 {
     unsigned int lun = 123324; 
     Char num[] = "012345678912";
     vector<char> VV;

     "1" ostringstream efficiency is lower than _itoa_s

     //ostringstream Lstrstream;
     lstrstream<<lun;                            Time consuming 6.875 seconds

     //char cc[12];
     _itoa_s (LUN, CC, a);                   Time consuming 0.063 seconds

     //"2" map[index]= value efficiency is lower than map.insert

     //mss[i] = "ABDFADAF";                        Time consuming 9.172 seconds
     //mss.insert (Make_pair (i, "ABDFADAF"));       Time consuming 7.454 seconds

     //"3" vector single push_back efficiency lower than Vector.insert
     //for (int n=0; n<12; n++)                    //time consuming 30.344 seconds
     / /{
     //    Vv.push_back (Num[n]);
     }
     //vv.insert (Vv.end (), &num[0], &num[0]+12);    Time consuming 3.079 seconds
 }
 c2 = Clock ();
 Double d = (double) (C2-C1)/clocks_per_sec;