help with using a set()!!

[huntermc101]

I have an additional txt file that i need to read into my cpp file by using a set. Im not understanding how to incorporate this into my code. any help would be great.

  #include "city.h"
  7 #include <iostream>
  8 #include <iomanip>
  9 #include <fstream>
 10 #include <sstream>
 11 #include <vector>
 12 using namespace std;
 13 
 14 vector<City*> cityvec;
 15 
 16 int main()
 17 { 
 18   ifstream inf("inputfile.txt");
 19   string city;
 20   float rainOne, rainTwo, totalrain;
 21   cout << "City\t\t total\n"
 22     << "--------------------\n"
 23     <<setprecision(1) << endl;
 24   
 25     while (!inf.eof())
 26     {
 27       inf >> rainOne;
 28       inf.ignore();
 29       getline(inf, city, ',');
 30       inf >> c;
 31       inf.ignore();
 32      City* ctyp;
 33      ctyp= new City(rainOne, city, raintwo);
 34      cityvec.push_back(ctyp);
 35      
 36      
 37      totalrain=(ctyp->getRainOne()+ctyp->getRainTwo());
 38      setw(21+(city.size()));
 39      
 40      
 41      cout << ctyp->getCityName();
 42      cout.width(19-City.size());
 43      cout <<' ' <<totalrain <<endl;
 44    }  
 45 return 0;
 46 }

[N85iE3v7]

Take a look here:

http://www.cplusplus.com/reference/set/set/

I bet they are asking you to replace the usage of the vector container for the set container, set is an associative container, and it won't accept duplicated entries.

// this is what you are using
vector<City*> cityvec;
// include <set>
// use std::set<City*> cityset; 

I would also supply a functor to your City class, so that the constructor of set knows how to sort it at every insertion. It is something simple like:

struct classcomp {
  bool operator() (const City1& c1, const City2& c2) const
     // return your own way of comparing City objects;  
};

Then you construct your set passing the above functor:

std::set<City*,classcomp> cityset;

You would usually use a set when you want to have unique entries and want it sorted automatically during the insertion. Please if you still have questions, post your city class here.

Hope it helps.

[N85iE3v7]

Hey

It is something like this

#include<set>
#include<iostream>
#include <string>

using namespace std;

class City
{
public:
City( float f1,
float f2,
string thecity);

string getCityName() ;
float getRainOne();
float getRainTwo() ;

private:

float rainOne;
float rainTwo;
string cityName;

};

City::City( float f1,
float f2,
string thecity
) : rainOne(f1), rainTwo(f2), cityName(thecity)
{
// for(int i=0;i<50;++i);
}

string City::getCityName()
{
return cityName;
}

float City::getRainOne()
{
return rainOne;
}

float City::getRainTwo()
{
return rainTwo;
}

template< class D >
struct comp
{
bool operator()( const D& c1, const D& c2) const
{
return ( c1->getCityName().length() > c2->getCityName().length() );
};

};

int main()
{

set<City*, comp<City*> > setContainer;
typedef set<City*, comp<City*> >::const_iterator ItCpp;

City* c1 = new City( 2.2, 2.3, "Piramboia");
City* c4 = new City( 3.3, 6.0, "Jarasdasdasdasdasdasdasdasdasd");
City* c2 = new City( 2.4, 2.3, "Carapicuiba");
City* c3 = new City( 2.4, 2.3, "Pindamongaba");

setContainer.insert( c1 );
setContainer.insert( c2 );
setContainer.insert( c3 );
setContainer.insert( c4 );

//for( auto it = setContainer.begin(); it != setContainer.end(); it++)// C++11
for( ItCpp it = setContainer.begin(); it != setContainer.end(); it++)// C++03
{
City* ptr = *it;
cout << "City: " << ptr->getCityName() << endl;
}

return 0;

}

A bit tricky , but I sorted the City class by its name length. Also, the pointer notation is messing. The const operator indicates that the variable referenced by the operator & ( an improved pointer reference that Cpp allows ) cannot be changed. The const after the method declaration simply means it won't change the value of any class members.

[Bourgond Aries]

Why use a compare struct when you can use an std::function<...>?

#include <set>
#include <functional>

int main()
{
    typedef std::function<bool(const int &, const int &)> cmpf;
    
    cmpf compare = [](const int& lhs, const int& rhs){return lhs < rhs;};
    std::set<int, cmpf> s(compare);
    
    return 0;
}

[N85iE3v7]

@Bourgond, agreed. I was just not sure if the OP was using a C++11 compliant compiler. Using lambda functions would confuse the Op even more, but I concur that is a clear and better solution.