C++ Tutorial/map multimap/map insert
Содержание
- 1 Duplicate keys are not allowed in a map
- 2 Insert a pair object directly
- 3 Insert a pair using function make_pair
- 4 Insert characters into map.
- 5 Insert key-value pairs into the map using value_type
- 6 Insert using an array-like syntax for inserting key-value pairs
- 7 Insert value pair to map
- 8 Use insert() to add an entry
- 9 use subscript operator to write value to a map
Duplicate keys are not allowed in a map
<source lang="cpp">#include <iostream>
- include <string>
- include <map>
- include <utility>
using namespace std; void show(const char *msg, map<string, string> mp); int main() {
map<string, string> phonemap; phonemap["A"] = "444-555-1234"; phonemap["B"] = "555-555-6576"; phonemap["C"] = "555-555-9843"; show("Here is the original map: ", phonemap); cout << endl; // Now, change the phone number for Ken. phonemap["B"] = "555 555-5555"; cout << "New number for Ken: " << phonemap["Ken"] << "\n\n"; // Create a pair object that will contain the result of a call to insert(). pair<map<string, string>::iterator, bool> result; // Duplicate keys are not allowed, as the following proves. result = phonemap.insert(pair<string, string>("B", "555-1010")); if(result.second) cout << "Duplicate added! Error!"; else cout << "Duplicate not allowed.\n"; show("phonemap after attempt to add duplicate key: ", phonemap); return 0;
} // Display the contents of a map<string, string> by using an iterator. void show(const char *msg, map<string, string> mp) {
map<string, string>::iterator itr; cout << msg << endl; for(itr=mp.begin(); itr != mp.end(); ++itr) cout << " " << itr->first << ": " << itr->second << endl; cout << endl;
}</source>
Insert a pair object directly
<source lang="cpp">#include <map>
- include <iostream>
using namespace std; typedef map <int, string> MAP_INT_STRING; typedef multimap <int, string> MMAP_INT_STRING; int main () {
MAP_INT_STRING mapIntToString; mapIntToString.insert (pair <int, string> (1000, "One Thousand")); cout << "The map contains " << mapIntToString.size (); cout << " key-value pairs. " << endl; cout << "The elements in the map are: " << endl; return 0;
}</source>
Insert a pair using function make_pair
<source lang="cpp">#include <map>
- include <iostream>
using namespace std; typedef map <int, string> MAP_INT_STRING; typedef multimap <int, string> MMAP_INT_STRING; int main () {
MAP_INT_STRING mapIntToString; mapIntToString.insert (make_pair (-1, "Minus One")); cout << "The map contains " << mapIntToString.size (); cout << " key-value pairs. " << endl; cout << "The elements in the map are: " << endl; return 0;
}</source>
Insert characters into map.
<source lang="cpp">#include <iostream>
- include <string>
- include <map>
using namespace std; int main() {
map<string, int> m; m.insert(pair<string, int>("A", 100)); m.insert(pair<string, int>("G", 300)); m.insert(pair<string, int>("B", 200)); return 0;
}</source>
Insert key-value pairs into the map using value_type
<source lang="cpp">#include <map>
- include <iostream>
using namespace std; typedef map <int, string> MAP_INT_STRING; typedef multimap <int, string> MMAP_INT_STRING; int main () {
MAP_INT_STRING mapIntToString; // Insert key-value pairs into the map using value_type mapIntToString.insert (MAP_INT_STRING::value_type (3, "Three")); cout << "The map contains " << mapIntToString.size (); cout << " key-value pairs. " << endl; cout << "The elements in the map are: " << endl; return 0;
}</source>
Insert using an array-like syntax for inserting key-value pairs
<source lang="cpp">#include <map>
- include <iostream>
using namespace std; typedef map <int, string> MAP_INT_STRING; typedef multimap <int, string> MMAP_INT_STRING; int main () {
MAP_INT_STRING mapIntToString; // Insert using an array-like syntax for inserting key-value pairs mapIntToString [1000000] = "One Million"; cout << "The map contains " << mapIntToString.size (); cout << " key-value pairs. " << endl; cout << "The elements in the map are: " << endl; return 0;
}</source>
Insert value pair to map
<source lang="cpp">#include <iostream> using std::cout; using std::endl;
- include <map> // map class-template definition
int main() {
std::map< int, double, std::less< int > > pairs; pairs.insert( std::map< int, double, std::less< int > >::value_type( 15, 2.7 ) ); pairs.insert( std::map< int, double, std::less< int > >::value_type( 30, 111.11 ) ); pairs.insert( std::map< int, double, std::less< int > >::value_type( 0, 1010.1 ) ); pairs.insert( std::map< int, double, std::less< int > >::value_type( 10, 22.22 ) ); pairs.insert( std::map< int, double, std::less< int > >::value_type( 25, 33.333 ) ); pairs.insert( std::map< int, double, std::less< int > >::value_type( 0, 77.54 ) ); // dup ignored pairs.insert( std::map< int, double, std::less< int > >::value_type( 20, 9.345 ) ); pairs.insert( std::map< int, double, std::less< int > >::value_type( 15, 99.3 ) ); // dup ignored cout << "pairs contains:\nKey\tValue\n"; // use const_iterator to walk through elements of pairs for ( std::map< int, double, std::less< int > >::const_iterator iter = pairs.begin(); iter != pairs.end(); ++iter ) cout << iter->first << "\t" << iter->second << "\n"; cout << endl; return 0;
}</source>
pairs contains: Key Value 0 1010.1 10 22.22 15 2.7 20 9.345 25 33.333 30 111.11
Use insert() to add an entry
<source lang="cpp">#include <iostream>
- include <string>
- include <map>
- include <utility>
using namespace std; void show(const char *msg, map<string, string> mp); int main() {
map<string, string> phonemap; phonemap["A"] = "444-555-1234"; phonemap["B"] = "555-555-6576"; phonemap["C"] = "555-555-9843"; show("Here is the original map: ", phonemap); phonemap["B"] = "555 555-5555"; cout << "New number: " << phonemap["B"] << endl; // Create a pair object that will contain the result of a call to insert(). pair<map<string, string>::iterator, bool> result; // Use insert() to add an entry. result = phonemap.insert(pair<string, string>("J", "555-9999")); if(result.second) cout << "J added."; show("phonemap after adding J: ", phonemap); return 0;
} // Display the contents of a map<string, string> by using an iterator. void show(const char *msg, map<string, string> mp) {
map<string, string>::iterator itr; cout << msg << endl; for(itr=mp.begin(); itr != mp.end(); ++itr) cout << " " << itr->first << ": " << itr->second << endl; cout << endl;
}</source>
use subscript operator to write value to a map
<source lang="cpp">#include <algorithm>
- include <iostream>
- include <map>
- include <utility>
using namespace std; int main( ) {
const char* word[] = { "A", "B", "C", "D","E" }; const char* clue[] = { "a", "b","c", "d","e" }; map<string,string> dictionary1; transform( word, word+sizeof(word)/sizeof(word[0]), clue,inserter( dictionary1, dictionary1.end() ),make_pair<string,string> ); cout << "There are " << dictionary1.size() << " words in the dictionary\n\n"; cout << "The clue for POPS is \"" << dictionary1["POPS"] << "\"\n" << "The clue for TAT is \"" << dictionary1["TAT"] << "\"\n" << "The clue for ESPO0 is \"" << dictionary1["ESPO0"] << "\"\n"; cout << "\nThere are " << dictionary1.size() << " words in the dictionary\n\n"; // use subscript operator to write value dictionary1["ESPO0"] = "Typo in name"; cout << "The clue for ESPO0 is \"" << dictionary1["ESPO0"] << "\"";
}</source>