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//DISPLAY 7.12 Sorting an Array
//Tests the procedure sort.
#include <iostream>
using namespace std;
void fill_array(int a[], int size, int& number_used);
//Precondition: size is the declared size of the array a.
//Postcondition: number_used is the number of values stored in a.
//a[0] through a[number_used  1] have been filled with
//nonnegative integers read from the keyboard.
void sort(int a[], int number_used);
//Precondition: number_used <= declared size of the array a.
//The array elements a[0] through a[number_used  1] have values.
//Postcondition: The values of a[0] through a[number_used  1] have
//been rearranged so that a[0] <= a[1] <= ... <= a[number_used  1].
void swap_values(int& v1, int& v2);
//Interchanges the values of v1 and v2.
int index_of_smallest(const int a[], int start_index, int number_used);
//Precondition: 0 <= start_index < number_used. Referenced array elements have
//values.
//Returns the index i such that a[i] is the smallest of the values
//a[start_index], a[start_index + 1], ..., a[number_used  1].
int main( )
{
cout << "This program sorts numbers from lowest to highest.\n";
int sample_array[20], number_used;
fill_array(sample_array, 20, number_used);
sort(sample_array, number_used);
cout << "In sorted order the numbers are:\n";
for (int index = 0; index < number_used; index++)
cout << sample_array[index] << " ";
cout << endl;
cout << "The smallest number is: " << sample_array[0] << endl;
cout << "The largest number is: " << sample_array[number_used1] << endl;
int total = 0;
for (int i = 0; i < total; i++)
{
total = total + sample_array[i];
}
cout << "The average is: " << total/number_used << endl;
system("PAUSE");
return 0;
}
//Uses iostream:
void fill_array(int a[], int size, int& number_used)
{
using namespace std;
cout << "Enter up to " << size << " nonnegative whole numbers.\n"
<< "Mark the end of the list with a negative number.\n";
int next, index = 0;
cin >> next;
while ((next >= 0) && (index < size))
{
a[index] = next;
index++;
cin >> next;
}
number_used = index;
}
void sort(int a[], int number_used)
{
int index_of_next_smallest;
for (int index = 0; index < number_used  1; index++)
{//Place the correct value in a[index]:
index_of_next_smallest =
index_of_smallest(a, index, number_used);
swap_values(a[index], a[index_of_next_smallest]);
//a[0] <= a[1] <=...<= a[index] are the smallest of the original array
//elements. The rest of the elements are in the remaining positions.
}
}
void swap_values(int& v1, int& v2)
{
int temp;
temp = v1;
v1 = v2;
v2 = temp;
}
int index_of_smallest(const int a[], int start_index, int number_used)
{
int min = a[start_index],
index_of_min = start_index;
for (int index = start_index + 1; index < number_used; index++)
if (a[index] < min)
{
min = a[index];
index_of_min = index;
//min is the smallest of a[start_index] through a[index]
}
return index_of_min;
}
 