How can I get all the unique keys in a multimap

0 votes

I have a multimap and I want to save all of the unique keys in it in a vector.

multimap<char,int> mymm;
  multimap<char,int>::iterator it;
  char c;

  mymm.insert(pair<char,int>('x',50));
  mymm.insert(pair<char,int>('y',100));
  mymm.insert(pair<char,int>('y',150));
  mymm.insert(pair<char,int>('y',200));
  mymm.insert(pair<char,int>('z',250));
  mymm.insert(pair<char,int>('z',300));

How can I accomplish this? 

There is a method for counting the number of items with a key, but none for counting the number of unique keys in a multimap.

Added: By unique, I mean all the keys in the multimap just once - they can be duplicated or appear only once in the multimap.

So unique keys here are - xy and z

Jun 22, 2022 in C++ by Nicholas
• 7,760 points
1,264 views

1 answer to this question.

0 votes

This method worked for me.

for( multimap<char,int>::iterator it = mymm.begin(), end = mymm.end(); it != end; it = mymm.upper_bound(it->first))

  {
      cout << it->first << ' ' << it->second << endl;
  }
answered Jun 27, 2022 by Damon
• 4,960 points

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