CODEWITHSUNDEEP
c++iterationmultimap
rsk82
rsk82

Reputation: 29377

how to loop multimap only to get first key-value pairs for every key?

For example if I have such mmap:

alice -> 30
bob -> 23
josh -> 20
josh -> 30
andy -> 40
andy -> 40

to get only this pairs:

alice -> 30
bob -> 23
josh -> 20
andy -> 40

Upvotes: 5

Views: 3181

Answers (2)

John Bandela
John Bandela

Reputation: 2436

Here is a short answer, but not the most efficient

multimap<string, int> mm;
// Add stuff to multimap

// Map with only the first items from multimap
map<string,int> m;

for(auto iter = mm.rbegin(); iter != mm.rend(); ++iter){
   m[iter->first] = iter->second;
}

This works because we start from the end. Thus any duplicate keys in multimap will overwrite the previous key in map. Since we start from the end, we should have the first key

Upvotes: 1

Viktor Sehr
Viktor Sehr

Reputation: 13099

This oughta do it as clean, and effective, as possible:

for(auto it = m.begin(); it != m.end(); it = m.upper_bound(it->first)) {
  std::cout << it->first << ":" << it->second << std::endl;
}

Upvotes: 9

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