Custom sort in C++ adding attributes

Asked By billy jones 260 points N/A Posted on - 05/13/2011

Hi,

I have a vector of objects defined as follows:

 

class items

{

public:

string name;

int cost;

int weight;

};

 

I need to sort it first on the basis of cost. If cost are equal on the basis of weight, if they are equal too. I need them in the alphabetic order.

 

I am doing some brute force loop, to sort them based on cost.

 

 

void Sorter(vector<items> &v)

{

bool done=false;

 

while(!done)

{

done=true;

for(int i=v.size()-1;i>0;–i)

{

if(v[i-1].cost>v[i].cost){swap(v[i-1],v[i]);done=false;}

}

}

}

 

But how do I add other attributes? They are just getting messy.

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• Question Category: C++

Best Answer by softwaresynthesis

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Answered By softwaresynthesis 0 points N/A #92759

Custom sort in C++ adding attributes

If you are learning the ways of sort, then yes it would be complicated. Just add every condition in the swap instead of just

 

If(v[i-1].cost>v[i].cost)

 

And if you are just doing this as a part of something big, then you should use the sort() function in algorithm. It is much faster and smoother.

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Answered By technical007 0 points N/A #92760

Custom sort in C++ adding attributes

Bill,

Bubble sort is not as quick as quick sort.

You should try that and yes, as software synthesis said, there is simply no need to re-invent the wheel. There is a sort function in algorithm. All you need to do is define in a comparator function.

To know how to use a comparator function, you can read this.

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• Posted on - 05/13/2011
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Answered By billy jones 260 points N/A #92761

Custom sort in C++ adding attributes

Thanks very much.

 

I know there is a function sort() in algorithm but I don't know how to use it with a comparator function.

 

How do I declare a comparator function?

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Answered By softwaresynthesis 0 points N/A #92762

Custom sort in C++ adding attributes

Bill,

It is very easy. Just like any other ordinary function. Its return type is blue and takes 2 parameters a and b.

Suppose a and b are 2 consecutive elements of the vector.

If a and b is in proper placements i.e a<b (for ascending) then return true, else return false.

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• Posted on - 05/13/2011
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Answered By billy jones 260 points N/A #92763

Custom sort in C++ adding attributes

But I have 3 properties to be considered;

• String name;
• Int cost;
• Int weight;

Do I need 3 comparator functions? or 1 to do all of them ? Then how many parameter would there be? 6?

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Answered By softwaresynthesis 0 points N/A #92765

Custom sort in C++ adding attributes

You don't need to pass all the properties. Just pass the two objects and access their properties, from within the function. Here is a simple comparator function to help you out

bool comparator(items a,items b)
{
    if(a.cost>b.cost)
        return false;
    if(a.cost<b.cost)
        return true;
    else if(a.weight>b.weight)
        return false;
    else if (a.weight<b.weight)
        return true;
    else if(a.name>b.name)
        return false;
    else
        return true;
}

Try this and I think you shall get it soon.

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Answered By billy jones 260 points N/A #92767

Custom sort in C++ adding attributes

Thanks a lot Software Synthesis. I got that finally. It's really amazing.

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Answered By softwaresynthesis 0 points N/A #92768

Custom sort in C++ adding attributes

You are most welcome.

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• Posted on - 05/14/2011
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