Rank Ordering A map<string, int>

I have map<string, int> which I want to order descending by the int value. Can Anyone Help? Perhaps with a pre-written rank ordering function.

Many Thanks
inghfsAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Infinity08Commented:
Then why not use a map<int, string> instead ???
0
inghfsAuthor Commented:
This is what I am currently doing with the map. I'm not sure it makes scence to use map<int, string>.

while (wordsfile >> s) {  
             
              if (occurrences[s] == 0)  
                        words.push_back(s);
             
              occurrences[s]++;                                
        }  
0
Infinity08Commented:
Well, there are two obvious solutions :

1) copy the data in a vector and sort the vector

http://www.cplusplus.com/reference/stl/vector/
http://www.cplusplus.com/reference/algorithm/sort.html

2) create a new map<int, string> (or probably a multimap since the ints can be duplicate), and fill it with the same data

http://www.cplusplus.com/reference/stl/multimap/


Note that you don't need to sort in descending order. The default sort is in ascending order, and you can just read the data from last to first element.
0
HTML5 and CSS3 Fundamentals

Build a website from the ground up by first learning the fundamentals of HTML5 and CSS3, the two popular programming languages used to present content online. HTML deals with fonts, colors, graphics, and hyperlinks, while CSS describes how HTML elements are to be displayed.

jkrCommented:
>>I'm not sure it makes scence to use map<int, string>.

It makes sense when it comes to have the different ordering for a certain situation. The idea is to keep the original map<string, int> to map the occurrances, but to use a map<int,string> temporarily to have the opposite ordering for the ranking, i.e.

map<string, int> occurances;
map<int,string> ranking;

// ... read values

while (wordsfile >> s) {  
             
              if (occurrences[s] == 0)  
                        words.push_back(s);
             
              occurrences[s]++;                                
        }  

//...

// now, get the ranking


map<string, int>::iterator i;

for (i = occurances.begin(); i != occurances.end(); ++i) {

    ranking.insert(map<int,string>::value_type(i->second,i->first)); // insert using the reverse
}

0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
itsmeandnobodyelseCommented:
>>>> or probably a multimap since the ints can be duplicate
That might give the overkill. If the int values are not unique (even for rankings some may share a rank) a multimap helps cause each int key can point to more than one value, but I never experienced a more uncomfortable interface than with a multimap. I strongly recommend to put key and value into a struct and use two std::set containers providing two different compare functions, where the first compares the (unique) string members while the second needs to compare the int member *and* the string member to guarantee uniqueness.  If you don't want to have redundancies you might store pointers rather than values.  

Regards, Alex
0
inghfsAuthor Commented:
ok I will have to look at this again but will be away for a few weeks - so please excuse continued silence.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
C++

From novice to tech pro — start learning today.