Check out example codes for "iterar en map". It will help you in understanding the concepts better.

Code Example 1

//traditional way (long)
for(map<string,int>::iterator it=m.begin(); it!=m.end(); ++it)
	if(it->second)cout<<it->first<<" ";
//easy way(short) just works with c++11 or later versions
for(auto &x:m)
	if(x.second)cout<<x.first<<" ";
//condition is just an example of use

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