reading arbitrary numbers from file and bubble sort them - c++

Question

i'm trying to write a program that reads numbers from a text file( 21 12 44 21 -5 63 0 ) to an array and bubble sort them in an descending order, and printing out only positive numbers. i have been trying for a while but what is displayed is not what i expect.
the contents of the text file are:
21 12 44 21 -5 63 0
the full code:
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <iomanip>
#include <conio.h>
using namespace std;
class bubble
{
public:
unsigned* arr;
int n;
//Constructor
bubble(const int& size) : n(size) { this->arr = new unsigned[n]; }
//function to read from file
void inputvf(istream &f)
{
//check if file is open
if (f.fail()) {
cout << "\n Error in openning file!!!";
exit(1);
}
for (int i = 0; i < n; i++)
f >> arr[i];
delete[] arr;
//close file
//f.close();
}
//Bubble sort function
void bubblesort()
{
for (int i = 1; i<n; i++)//for n-1 passes
{
for (int j = 0; j<n - 1; j++)
{
if (arr[j] < arr[j + 1])
{
int temp;
temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
}
}
void display()
{
cout << endl;
cout << "----------------------\n";
cout << "Sorted array elements \n";
cout << "----------------------\n";
if (arr >= 0){
for (int j = 0; j < n; j++)
cout << arr[j] << endl;
}
}
};
int _tmain(int argc, _TCHAR* argv[])
{
bubble list(7);
ifstream file("Text.txt");
list.inputvf(file);
list.bubblesort();
list.display();
_getch();
return 0;
results after i run the code:
4277075694
1
4261281277
2880154539
2880154539
4277075694
0
what am i doing wrong??? please help
this is the new code(below):
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <iomanip>
#include <conio.h>
using namespace std;
class bubble
{
public:
//Array of integers to hold values
int* arr;
//Number of elements in array
int n;
//Constructor
bubble(const int& size) : n(size) { this->arr = new int[n]; }
//function to read from file
void inputvf(istream &f)
{
//check if file is open
if (f.fail()) {
cout << "\n Error in openning file!!!";
exit(1);
}
for (int i = 0; i < n; i++)
f >> arr[i];
//delete[] arr;
//close file
//f.close();
}
//Bubble sort function
void bubblesort()
{
for (int i = 1; i<n; i++)//for n-1 passes
{
for (int j = 0; j<n - 1; j++)
{
if (arr[j] < arr[j + 1])
{
int temp;
temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
}
}
void display()
{
cout << endl;
cout << "----------------------\n";
cout << "Sorted array elements \n";
cout << "----------------------\n";
if (arr >= 0){
for (int j = 0; j < n; j++)
cout << arr[j] << endl;
}
}
};
int _tmain(int argc, _TCHAR* argv[])
{
bubble list(7);
ifstream file("Text.txt");
list.inputvf(file);
list.bubblesort();
list.display();
_getch();
return 0;
}

Answer 1

Two problems:
In inputvf:
delete[] arr;
You should not delete the array at this point - you haven't even started using it yet.
This declaration:
unsigned* arr;
means that all of your input is unsigned, which means -1 is read as 4294967291 and thus will be treated as a large number. Change your array to a normal int and then use an if test to ignore negative numbers when outputting.