C + + Learning notes (eight)-map

Map<key, Value> is ordered by key, key cannot be duplicated.

1. Map.lower_bound (): Press key to find, if the found key exists, return to that location, if there is no value returned greater than the minimum key location

1#include <iostream>2#include <map>3 using namespacestd;4 5 intMain ()6 {7std::map<Char,int>Mymap;8std::map<Char,int>:: iterator Itlow,itup;9 Tenmymap['a']= -; Onemymap['b']= +; Amymap['b']= -;//The key value is not duplicated, and the value of B is updated to -mymap['C']= the;//values of value can be repeated -mymap['D']= the; themymap['e']= -; -  -    for(std::map<Char,int>::iterator It=mymap.begin (); It!=mymap.end (); ++it) -Std::cout << It->first <<"="<< It->second <<'\ n'; +cout<<Endl; -    　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 //This procedure actuallycannot be inserted successfully because key=b already exists and value is not updated +Itlow=mymap.lower_bound ('b');//if the key value B exists, Itlow points to B, otherwise it points to the location of the smallest key larger than B AMymap.insert (itlow,std::map<Char,int>::value_type ('b', +)); //Insert map< ' B ',40> to the position pointed to by Itlow  at  -    for(std::map<Char,int>::iterator It=mymap.begin (); It!=mymap.end (); ++it) -Std::cout << It->first <<"="<< It->second <<'\ n'; -cout<<Endl; -  -   CharC='a'; in    while(1) -{//Enter a character and insert toCin>>C;  +Itlow =Mymap.lower_bound (c); -     if(Itlow! =mymap.end ()) thecout<<"Insert"<<c<<"To Position:"<<itlow->first<<" , "<<itlow->second<<'\ n'; *Mymap.insert (Itlow, map<Char,int>::value_type (c, the+c)); $      for(std::map<Char,int>::iterator It=mymap.begin (); It!=mymap.end (); ++it)Panax NotoginsengStd::cout << It->first <<"="<< It->second <<'\ n'; -cout<<Endl; the   } the   return 0; + }

Output Result:

1 A =2 B = +3 C =4 d =5 e =6 7 A =8 B = +9 C =Ten d = One e = A  - d //did not insert successfully, D is the value  of the original - Insert D to Position:d, the A = - B = + - C = - d = + e = -  + z //insertion position in Map.end  A A = at B = + - C = - d = - e = - z = 282 -  in x - Insert X to position:z, 282 to A = + B = + - C = the d = * e = $ x = 280Panax Notoginsengz = 282

2. Map.key_comp (), returns true only if the first parameter is less than the second one.

The function return value is bool type, the input is two key value, Key_comp () (A, B), 1 is returned when a<b, otherwise 0 is returned.

1#include <iostream>2#include <map>3 using namespacestd;4 intMain ()5 {6std::map<Char,int>Mymap;7 8mymap['a'] = -;9mymap['C'] = -;Tenmymap['x']=101; Onemymap['y']=203; Amymap['Z']=103; -  -Std::cout <<"Mymap contains:\n"; themap<Char,int>::iterator it =Mymap.begin (); -    for(it = Mymap.begin (); It!=mymap.end (); it++) -cout<<it->first<<"="<<it->second<<'\ n'; -cout<<Endl; +  -map<Char,int>::iterator pit =Mymap.begin (); +pit++; Apit++;//Pit points to the third element map<x,101> at  -it =Mymap.begin (); -    for(it = Mymap.begin (); It!=mymap.end (); it++) -   { -cout<<"Key Comp Result:"<<mymap.key_comp (It->first, Pit->first) <<Endl; -   } incout<<Endl; -   return 0; to}

Results:

1 Mymap contains:2A = -3c = -4x =1015y =2036z =1037 8Key Comp Result:19Key Comp Result:1TenKey Comp Result:0 //At this time It=pit  OneKey Comp Result:0 AKey Comp Result:0

C + + Learning notes (eight)-map