C++ Array not sorting properly - c++

Question

I wanted to sort nuggets by unit price, so I made a class Nugget with the variables quant, and price, then made a double unit, which is price/quant. The nuggets come in 4, 6 and 9 packs
When I input 10, 10, and 10, for the price of each, I should get a sorted array of 9pack, 6pack and then a 4pack, because 10/9 is less than 10/6 and 10/4. But thats not the case.
#include <iostream>
using namespace std;
class Nugget {
public:
int price;
int quant;
double unit;
Nugget(int price, int quant) {
this->price = price;
this->quant = quant;
this->unit = price/quant;
}
};
int main(){
int n4,n6, n9;
cin >> n4 >> n6 >> n9;
Nugget* nuggetArr[3] = {new Nugget(n4,4), new Nugget(n6,6), new Nugget(n9,9)};
for (int i = 0; i < 3; ++i) {
for (int j = 0; j < 3; ++j) {
if (nuggetArr[j]->unit > nuggetArr[i]->unit) {
Nugget* temp = nuggetArr[i];
nuggetArr[i] = nuggetArr[j];
nuggetArr[j] = temp;
}
}
for (int j = 0; j < 3; j++)
cout << nuggetArr[j]->quant << ' ';
cout << endl << endl;
}
for (int i = 0; i<3; ++i)
cout << nuggetArr[i]->quant << ' ';
return 0;
};

Answer 1

What sorting algorithm you want to use?
If you swap nuggetArr[i] for nuggetArr[j] you should ensure that i < j for ascending or i > j for descending order.
For example:
for (int i = 0; i < 3; ++i) {
for (int j = i + 1; j < 3; ++j) {
if (nuggetArr[j]->unit > nuggetArr[i]->unit) {
Nugget* temp = nuggetArr[i];
nuggetArr[i] = nuggetArr[j];
nuggetArr[j] = temp;
}
}
Your code moves around objects (nuggets) not keeping some order.
For example you swap nuggetArr[1] for nuggetArr[2] and then nuggetArr[2] for nuggetArr[1].
FYI this is similar to Selection sort.

Answer 2

C++ uses a wierd way of casting here. It uses integers until assignement, so the unit value will be an integer even though you used double. If you make the following changes you will find that it will work (Please note that this is just to illustrate the point and is not good to use this because of precision):
...
double price;
double quant;
...
this->unit = this->price/this->quant;
...
Hope this helps
To be more precise as a note if a,b are integers then a/b will be an integer by default and after the division will it only be cast as a double.