[C++]Sorting objects by class member's value - c++

Question

In the code shown below, in the function void printExpensiveThanT(..) i'm supposed to print out the destination, distance and the price for the offers which are more expensive than the offer T in the function, sorted in ascending order by the distance value.
I'm not sure what should i use to sort them, i experimented something with vectors but it didn't work out so i deleted it.
Any help would be appreciated.
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
class Transport {
protected:
char destination[100];
int basePrice;
int distance;
public:
Transport() {}
Transport(char *destination, int basePrice, int distance) {
strcpy(this->destination, destination);
this->basePrice = basePrice;
this->distance = distance;
}
virtual ~Transport() {}
virtual int priceTransport() = 0;
friend bool operator<(const Transport &t1, const Transport &t2) {
return t1.distance<t2.distance;
}
int getDistance(){ return distance; }
char *getDestination() { return destination; }
int getPrice() { return basePrice; }
};
class AutomobileTransport : public Transport {
private:
bool ifDriver;
public:
AutomobileTransport() {}
AutomobileTransport(char *destination, int basePrice,int distance, bool ifDriver) : Transport(destination,basePrice,distance) {
this->ifDriver = ifDriver;
}
void setIfDriver(bool ifDriver) {
this->ifDriver = ifDriver;
}
bool getIfDriver() {
return ifDriver;
}
int priceTransport() {
if(ifDriver) {
basePrice+=basePrice*20/100;
}
return basePrice;
}
friend bool operator<(const AutomobileTransport &a1, const AutomobileTransport &a2) {
return a1.distance<a2.distance;
}
};
class VanTransport: public Transport {
private:
int passengers;
public:
VanTransport() {}
VanTransport(char *destination, int basePrice, int distance, int passengers) : Transport(destination, basePrice, distance) {
this->passengers = passengers;
}
void setPassengers(int passengers) {
this->passengers = passengers;
}
int getPassengers() {
return passengers;
}
int priceTransport() {
for(int i = 0; i < passengers; i++) {
basePrice-=200;
}
return basePrice;
}
friend bool operator<(const VanTransport &k1, const VanTransport &k2) {
return k1.distance<k2.distance;
}
};
void printExpensiveThanT(Transport **offers,int n,AutomobileTransport &T) {
Transport *tmp;
for(int i = 0; i <= n; i++){
if(offers[i]->priceTransport() > T.priceTransport())
cout<<offers[i]->getDestination()<<" "<<offers[i]->getDistance()<<" "<<offers[i]->getPrice()<<endl;
}
}
int main() {
char destination[20];
int type,price,distance,passengers;
bool driver;
int n;
cin>>n;
Transport **offers;
offers=new Transport *[n];
for (int i=0; i<n; i++) {
cin>>type>>destination>>price>>distance;
if (type==1) {
cin>>driver;
offers[i]=new AutomobileTransport(destination,price,distance,driver);
} else {
cin>>passengers;
offers[i]=new VanTransport(destination,price,distance,passengers);
}
}
AutomobileTransport at("Ohrid",2000,600,false);
printExpensiveThanT(offers,n,at);
for (int i=0; i<n; i++) delete offers[i];
delete [] offers;
return 0;
}

Answer 1

Since you're dealing with pointers, the easiest thing to do is to use std::vector and std::sort:
#include <vector>
//...
void printExpensiveThanT(Transport **offers, int n, AutomobileTransport &T)
{
std::vector<Transport*> sortedVect;
for (int i = 0; i < n; i++)
{
if (offers[i]->priceTransport() > T.priceTransport())
sortedVect.push_back(offers[i]); // add this item to the vector
}
// sort the vector based on the dereferenced pointers and their respective
// operator <
std::sort(sortedVect.begin(), sortedVect.end(),
[](Transport* left, Transport* right) { return *left < *right; });
// print out the values
for (auto it : sortedVect)
cout << (*it).getDestination() << " " << (*it).getDistance() << " " << (*it).getPrice() << "\n";
}
Also, your original code looped one more than it should (i <= n was wrong).
Edit:
If your compiler doesn't support the C++ 11 syntax, here is an alternate solution:
#include <vector>
//...
bool Sorter(Transport* left, Transport* right)
{ return *left < *right; }
void printExpensiveThanT(Transport **offers, int n, AutomobileTransport &T)
{
std::vector<Transport*> sortedVect;
for (int i = 0; i < n; i++)
{
if (offers[i]->priceTransport() > T.priceTransport())
sortedVect.push_back(offers[i]); // add this item to the vector
}
// sort the vector based on the dereferenced pointers and their respective
// operator <
std::sort(sortedVect.begin(), sortedVect.end(), Sorter);
// print out the values
std::vector<Transport*>::iterator it = sortedVect.begin();
while (it != sortedVect.end())
{
cout << (*it).getDestination() << " " << (*it).getDistance() << " " << (*it).getPrice() << "\n";
++it;
}
}