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I have an array of objects. I want to sort the array of a
given numeric value that exists in each of the objects. Suppose the
array of objects is called student and the numeric value I want to
sort the array based on the member is called "rollno".
ex:
class student{
int rollno;
int name;
int status;
};
student obj[10]
here, I have to sort obj of 10objects, based on rollno.

Please give your suggestion for any fast method?

On 19 Feb, 13:39, spl <splender....@gmail.com> wrote:
> I have an array of objects. I want to sort the array of a
> given numeric value that exists in each of the objects. Suppose the
> array of objects is called student and the numeric value I want to
> sort the array based on the member is called "rollno".
> ex:
> class student{
> int rollno;
> int name;
> int status;};
>
> student obj[10]
> here, I have to sort obj of 10objects, based on rollno.
>
> Please give your suggestion for any fast method?

Make an operator< for student that returns whether one student's
rollno is larger than the other, and call std::sort(obj, obj+10).
Or make a free function or function object functionally equivalent to
operator<, and pass it to std::sort.

On Feb 19, 1:39 pm, spl <splender....@gmail.com> wrote:
> I have an array of objects. I want to sort the array of a
> given numeric value that exists in each of the objects. Suppose the
> array of objects is called student and the numeric value I want to
> sort the array based on the member is called "rollno".
> ex:
> class student{
> int rollno;
> int name;
> int status;};
>
> student obj[10]
> here, I have to sort obj of 10objects, based on rollno.
>
> Please give your suggestion for any fast method?
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

class student{

public:
// added c-tor
student(int r,int n, int s):rollno(r),name(n),status(s) { }
int getRollno() const { return rollno;}
int getName() const { return name;}
int getStatus() const { return status;}

private:

int rollno;
int name;
int status;
};

bool compare(const student& x, const student& y) {
return x.getRollno() < y.getRollno();
}

int main(){
vector<student> students;
student s1(10,20,30);
student s2(40,50,60);
student s3(25,85,9;
students.push_back(s1);
students.push_back(s2);
students.push_back(s3);

sort(students.begin(),students.end(),compare);
for(vector<student>::const_iterator iter=students.begin();
iter!=students.end();++iter)
std::cout << (*iter).getRollno() << '\t' << (*iter).getName() <<
'\t' << (*iter).getStatus() << '\n';

return 0;
}

Hope this helps a bit,

Rgds,
Here is a very primitive example with the compare that you can supply
to the STL sort

"spl" <> a écrit dans le message de news:
818778ec-863c-4e06-ad32-ec8a4d6d7457...oglegroups.com...
>I have an array of objects. I want to sort the array of a
> given numeric value that exists in each of the objects. Suppose the
> array of objects is called student and the numeric value I want to
> sort the array based on the member is called "rollno".
> ex:
> class student{
> int rollno;
> int name;
> int status;
> };
> student obj[10]
> here, I have to sort obj of 10objects, based on rollno.
>
> Please give your suggestion for any fast method?

class student {
int rollno;
int name;
int status;
public: // operator< must be public, rollno needs not
bool operator<(student s const&) const { return rollno < s.rollno; }
}

int main()
{
student obj[10]
// Now I wonder how you populate obj since your members are private....
// You probably want everything to be public...
// Suppose obj is filled correctly as you want....
std::sort(obj,obj+10);
// now obj is sorted
return 0;
}

Note that if you want to sort your objects based on anything else than
rollno, you will have to supply a sorting function.

-----
Eric Pruneau