Use multimap to store key/value pairs in which duplicates might occur. - C++ STL

C++ examples for STL:multimap

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Introduction

This program uses a multimap to store names and phone numbers. It allows one name to be associated with more than one phone number.

Demo Code

#include <iostream>
#include <map>
#include <string>
using namespace std;
void shownumbers(const char *n, multimap<string, string> mp);
int main()//from  w  w w .  j  a va 2  s.c  o  m
{
   multimap<string, string> phonemap;
   // Insert elements by using operator[].
   phonemap.insert(pair<string, string>("Tom", "Home: 555-1111"));
   phonemap.insert(pair<string, string>("Tom", "Work: 555-1112"));
   phonemap.insert(pair<string, string>("Tom", "Cell: 555-1113"));
   phonemap.insert(pair<string, string>("Jane", "Home: 314 555-2226"));
   phonemap.insert(pair<string, string>("Jane", "Cell: 314 555-2222"));
   phonemap.insert(pair<string, string>("Ken", "Home: 660 555-3333"));
   phonemap.insert(pair<string, string>("Ken", "Work: 660 555-3330"));
   phonemap.insert(pair<string, string>("Ken", "Cell: 217 555-3335"));
   // Show all phone numbers for Tom, Jane, and Ken
   shownumbers("Tom", phonemap);
   cout << endl;
   shownumbers("Jane", phonemap);
   cout << endl;
   shownumbers("Ken", phonemap);
   cout << endl;
   // Now remove all phone numbers for Ken:
   cout << "Removing all numbers for Ken.\n";
   int count = phonemap.erase("Ken");
   cout << count << " elements have been removed.\n\n";
   cout << "After removing Ken, attempt to find phone number fails:\n";
   shownumbers("Ken", phonemap);
   return 0;
}
// Show all numbers for a given name.
void shownumbers(const char *n, multimap<string, string> mmp) {
   multimap<string, string>::iterator itr;
   // Find the first matching key.
   itr = mmp.find(n);
   // If the key was found, then display all phone numbers
   // that have that key.
   if(itr != mmp.end()) {
      cout << "Here are the numbers for " <<  n << ": " << endl;
      do {
         cout << "  " << itr->second << endl;
         ++itr;
      } while (itr != mmp.upper_bound(n));
   }
   else
      cout << "No entry for " << n << " found.\n";
}

Result


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