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How to sort a list with objects.

Dezibil Ad (16)
Hi guys, I have a problem, I wanted to sort the numbers of ingredients.
I tried several methods but have not reached a result. I've searched on the internet, I found an example, but I don't know how to make with "greater" like this "http://www.java2s.com/Tutorial/Cpp/0340__list/sortlistwithuserdefinedobjectswithgreater.htm" I don't get it... If someone can explain me with an easy path or method.
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 #include<iostream>
#include<list>
using namespace std;
class Milkshake{
private:
    string name;
    int ingredients;
public:
    Milkshake(string n="",int ing=0)
    {
        name=n;
        ingredients=ing;
    }
    void print()
    {
        cout<<"Name: "<<name<<endl;
        cout<<"ingredients: "<<ingredients<<endl;
    }
};
int main()
{
    Milkshake d1("Yas",40);
    Milkshake d2("Ord",2);
    Milkshake d3("Das",25);
    d1.print();
    list<Milkshake>myList;
    myList.push_front(d1);
    myList.push_front(d2);
    myList.push_front(d3)
    myList.sort();

}
Arslan7041 (753)
First you need to define what "sorting" means for your objects. Are you sorting alphabetically by 'name', or numerically by number of 'ingredients'.

Once you've decided that, you just need to make either a function or an overloaded parenthesis operator which implements your type of sort.

Take a look at this for some inspiration: http://www.cplusplus.com/reference/algorithm/sort/
Dezibil Ad (16)
I want to do both, but first I want to do sorting of ingredients .
When you said an overloaded parenthesis operator you speak about that:
bool operator()( Milkshake &a)
{
return(ingredients>a.ingredients;
}
I tried something but doesn't work.
Last edited on
coder777 (8444)
I tried something but doesn't work.
The operator for sort() is this:
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class Milkshake
{
...
public:
    bool operator<(const Milkshake &a) const
    {
      return (ingredients < a.ingredients); // (a.ingredients < ingredients)
    }
...
};

..

[EDIT]
std::sort(myList.begin(), myList.end());
// In case of list:
myList.sort();
Last edited on
Dezibil Ad (16)
TheSmallGuy, thank you man for your example, you are a savior of lives, now I have an idea how to do. Thank you all for help.
Dezibil Ad (16)
But I have a question, can I ask you?
Dezibil Ad (16)
I sent you a pm.
Last edited on
keskiverto (10402)
TheSmallGuy wrote:
P.S : std::list::sort() does not seem to be well supported by my compiler.

It is not your compiler. The std::sort requires random-access iterators. The std::list does not have them.
See http://www.cplusplus.com/reference/algorithm/sort/
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