CODEWITHSUNDEEP
c++arrayscountdistinct
Sherifftwinkie
Sherifftwinkie

Reputation: 391

Distinct number of strings in an array

UPDATED WITH FIX

I want to return only the number of unique entries in my array. The array contains a string variable that represents IP address. If there are 10 of them, but of 3 different kinds I just want to return 3. I have been at this all day and can't seem to figure out a solution that works. My code:

Original code

int getUnique(Visitors info[], string url, string startDate, string endDate){

int count = 0;

string temp;

for(int i = 0 ; i < N ; i++){

    if(url == info[i].URL && (dateChecker(startDate, endDate, info[i].dateAccessed))){



    }

}

return count;

}

Updated code

int getUnique(Visitors info[], string url, string startDate, string endDate){

set<string> ips;

for(int i = 0 ; i < N ; i++){

    if(url == info[i].URL && (dateChecker(startDate, endDate, info[i].dateAccessed))){

       ips.insert(info[i].IP);

    }

}

return ips.size();

}

The first if checks whether the matching URL does in fact match, and the dateChecker just makes sure that the date that the particular IP went to that URL is in between the 2 passed dates (startDate and endDate). How do I get the number of different IPs under these conditions?

Upvotes: 2

Views: 1379

Answers (4)

alexrider
alexrider

Reputation: 4463

As already mentioned you need to use std::set however there is no need to manually iterate array, since std::map accepts iterators to range it should be constructed from. Thus 

std::map<std::string> unique(strinvec.begin(), stringvec.end());

Should do the trick.
And if you need to know only count of unique elements, you may use even shorter notation. 

size_t unique_count = std::map<std::string>(strinvec.begin(), stringvec.end()).size();

Upvotes: 1

Shafik Yaghmour
Shafik Yaghmour

Reputation: 158459

You could use a std::set to keep track of unique strings:

std::set<std::string> mySet ;

for each iteration just do:

mySet.insert( info[i].IP) ;

and at the end:

return mySet.size() ;

Upvotes: 1

masoud
masoud

Reputation: 56479

Use std::set, it stores items uniquely and it's efficient:

std::set<string> ips;

for (int i=0; i<N; i++)
  ips.insert(info[i].IP);

int unique_ips = ips.size();

Upvotes: 2

stardust
stardust

Reputation: 5988

You can do this lazily with set

std::set<string> uniq;
if(url == info[i].URL && (dateChecker(startDate, endDate, info[i].dateAccessed))){
        uniq.insert(info[i].URL);
}

return uniq.size();

Upvotes: 1

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