C ++ Class＆.H Sorting

Question

Good evening experts and gurus !!

I have an array object that record the following..

This is at record.h

Class Record
{
private:
string name;
int data;
float valueData;
public:
bool operator<(const Record&) const;
}

and the constructor are created at record.cpp

record.cpp i added this

bool Record::operator<(const Record& rhs) const
{
return valueData < rhs.valueData;
}

At main.cpp I created record Array of Size 10

#include "record.h"

Record rec[10];

I did

sort(&rec[0], &rec[2]);

but nothing seems changing or sorted .. i got 3 element , rec[0], rec[1], rec[2] and i want sort them ,but they are of another header file record.h & its record.cpp which describe above.

Original Question Next is i recorded several value to the object

and now rec got 3 index

rec[0]
name = "jack1"
data = 1
valueData = 20

rec[1]
name = "jack2"
data = 2
valueData = 15

rec[2]
name = "jack3"
data = 3
valueData = 25

What i want to achieve is do a sort that can rearrange this array by valueData highest ascending form so.. it will be

rec[2] then rec[0] then rec[1] ..

but i wanna sort by class array object. and re-arrange the value together , how do i achieve this.

the 3 value is private, so i not sure where do i create the sort function, at main.cpp or at record.cpp , next is how do i sort it so it can output in the way below..

-- Highest to lowest --
1) Name: Jack3, Data = 3, Value =25
2) Name: Jack1 , Data =1 , Value = 20
3) Name: Jack2, Data = 2, Value = 15

Thanks for all help and guide!!

Answer 1

Do this instead:

sort(&rec[0], &rec[3]);

You were only sorting the 1st two elements, because the 2nd iterator in a range defined by an iterator pair by convention always points one past the end of the range you want to operate on.

Answer 2

Use std::sort in conjunction with something that compares two Record s. There are at least 3 ways to provide this compoarison.

1: Implement an operator< on Record :

class Record
{
public:
  bool operator<(const Record& rhs) const
  {
    return valueData < rhs.valurData;
  }
};

...then:

sort(&rec[0], &rec[10]);

2: Provide a functor :

struct compare_records : public std::binary_function<bool, Record, Record>
{
  bool operator()(const Record& lhs, const Record& rhs) const
  { 
    return lhs.valueData < rhs.valueData;
  }
};

...then:

sort_if(&rec[0], &rec[10], compare_records());

3: (If you have a C++11 compiler) Use a lambda:

sort_if(&rec[0], &rec[10], [](const Record& lhs, const Record& rhs) -> bool
{
  return lhs.vaklueData < rhs.valueData;
});

EDIT:

Here is a complete sample that shows how to use the first method:

#include <cstdlib>
#include <map>
#include <algorithm>
using namespace std;

class Record
{
public:
    string name;
    int data;
    float valueData;
public:
    bool operator<(const Record& rhs) const
    {
        return valueData < rhs.valueData;
    }
};

int main()
{
    Record rec[10];
    rec[0].name = "jack1";
    rec[0].data = 1;
    rec[0].valueData = 20;

    rec[1].name = "jack2";
    rec[1].data = 2;
    rec[1].valueData = 15;

    rec[2].name = "jack3";
    rec[2].data = 3;
    rec[2].valueData = 25;

    sort(&rec[0], &rec[3]);

    bool bk = true;
}