C++ Sorting Class Array - c++

Question

C++ Sorting Array Class
I have an array object that record the following..
This is at classone.h
ClassOne
{
string name;
int data;
float valueData;
}
and the constructor are created at classone.cpp
At main.cpp I created ClassOne Array of Size 10
#include "classone.h"
ClassOne cone[10];
Next is i recorded several value to the object
and now ClassOne got 3 objects
cone[0]
name = "hello"
data = 1
valueData = 20
cone[1]
name = "panda"
data = 2
valueData = 15
cone[2]
name = "joe"
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
cone[2] then cone[0] then cone[1] ..
but the issue if i use bubble sort , i tried google and find some, they are sorting by e.g int a[]={9,6,5,23,2,6,2,7,1,8};
but i wanna sort by class array object. and re-arrange the value together , how do i achieve this.
So when i cout it will be
-- Highest to lowest --
1) Name: Joe , Data = 3, Value =25
2) Name: Hello , Data =1 , Value = 20
3) Name: Panda, Data = 2, Value = 15
Thanks for all help and guide!!

Answer 1

The easiest way is to use the standard library:
#include <algorithm>
std::sort(cone, cone + 10,
[](ClassOne const & a, ClassOne const & b) -> bool
{ return a.value < b.value; } );
If you're willing to define a comparison operator globally, you don't even need the lambda:
bool operator<(ClassOne const & a, ClassOne const & b)
{
return a.value < b.value;
}
std::sort(cone, cone + 10);
Or you could make the comparator a member function. Or you could give the comparator function a custom name and pass that as the third argument of sort. This might be a good idea in the case where the comparison is specific to your situation and not "natural":
bool ValueCmp(ClassOne const & a, ClassOne const & b)
{
return a.value < b.value;
}
std::sort(cone, cone + 10, ValueCmp);
The last version is useful if you don't have C++11 support (for lambdas, as in the first case), or if you want to reuse the comparator in multiple different situations.

Answer 2

Use std::sort and a suitable sort function/functor:
bool comp(const ClassOne& lhs, const ClassOne& rhs)
{
return lhs.valueData < rhs.valueData;
}
std::sort(cone, cone+10, comp);
or, in C++11,
std::sort(std::begin(cone), std::end(cone), comp);

Answer 3

You can make a struct that implements the operator < method that std::sort in the <algorithm> header uses to sort iterated items.
struct One {
string name;
int data;
float valueData;
bool operator < (const one &a) const{
return valueData <a.valueData;
}
};
then all you have to do is to make an array of this struct and sort it using the sort function

Answer 4

Look at your Bubble sort source. At some point, it will be comparing one int to another, probably with either the less than operator (<) or the greater than operator (>). That's where the sort function determines the relative order of those two items. By repeating that comparison many times, the sort function is able to determine the total order of the collection.
You need to replace that operation with your own comparison function. A function that takes two objects of your class, and returns true if the first should be considered less than the second, false if the second should be considered less than the first, and false if they should be considered equivalent.

Answer 5

You must define a comparison operator for your class. How you determine whether one object is less than another isn't clear from your question.

Answer 6

Try this
...
....
void ClassOne::sort(ClassOne *obj,int n)
{
ClassOne temp;
int i, j;
for (i = 0; i < n; i++)
for (j = n - 1; j > i; j--)
if (obj[j].valueData <obj[j - 1].valueData )
{
temp = obj[j];
obj[j] = obj[j - 1];
obj[j - 1] = temp;
}
}
...
int main()
{
ClassOne obj[3],a;
for(int i=0;i<3;i++)
obj[i].readdata();
a.sort(obj,3);
...
}