Sorting an Array of Pointers to Objects

Question

I am trying to sort an Array of pointers to objects by name but i don't know if im going the right way with this. Here is my code so far...

main

Person *personArray[3]; //pointers to person objects

personArray[0] = new Employee("Bill", 1200);
personArray[1] = new Customer("Steve");
personArray[2] = new Employee("Bill", 1200);

Person *tempArray[3];
string temp1;

for(int i=3-1;i>0;i--) 
{
    int min = 0;
    for(int j=1;j<i;j++)
    {
        if(*tempArray[j] < *personArray[min])
        {
            min = j;
        }
    }
  temp1 = tempArray[min]->printname();
  tempArray[min] = tempArray[i];
  tempArray[i] = temp1;
}

class Person
    {
    public:
      Person(string); 
      virtual void printname() = 0;
      bool operator <(const Person& name1) const;
      bool operator ==(const Person& name1) const;

    protected:
      string name;
    };

    bool Person::operator <(const Person& name1) const
    {
       return (this->name < name1.name);
    }
    bool Person::operator ==(const Person& name1) const
    {
       return (this->name == name1.name);
    }

    void Person::printname()
    {
      cout << "Name: " << name << endl;
    }

Are you allowed to use standard library algorithms? If so, use std:sort with a custom predicate. — juanchopanza
– juanchopanza, Commented Feb 12, 2014 at 21:32
i dont think so, we were told to look up string::compare and use overloaded operators — Brumbles
– Brumbles, Commented Feb 12, 2014 at 21:36

rendon · Accepted Answer · 2014-02-12 21:47:45Z

1

I think this line is the problem:

if(*tempArray[j] < *personArray[min])

It should be:

if(*personArray[j] < *personArray[min])

Because tempArray hasn't been initialized at this point.

Even more, a temporary object should be sufficient, not an entire array.

And these lines...

temp1 = tempArray[min]->printname();
tempArray[min] = tempArray[i];
tempArray[i] = temp1;

too. tempArray has nothing, it should be something like this:

temp1 = personArray[min]->printname();
personArray[min] = personArray[i];
personArray[i] = temp1;

BTW, temp1 should be the same type of your objects (not string).

edited Feb 12, 2014 at 21:47

answered Feb 12, 2014 at 21:40

rendon

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4 Comments

Brumbles Over a year ago

How could i use a temporary object if there different derived classes?

rendon Over a year ago

Try with a Person pointer, I think the other objects derive from this. Isn't it?

Brumbles Over a year ago

Yeah but person is an abstract class and can't be instantiated

Brumbles Over a year ago

Ok i have it working but its sorting them in reverse alphabetical order

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