How to do selection sort? - c++

Question

Count all the records from the file "8.dat". To read each individual recording perform dynamic memory capture.
Sort the records to different keys:
Item number (ascending);
The cost (descending);
Number of stock (descending).
Use selection sort
Total sorting will be done 12 times, each time the array is sorted in its original condition.
For each case count of comparisons to and permutations.
Below code implements insertion sort. Twice, without saying so much.
I need to use selection sort. How to do selection sort?
#include <iostream>
#include <fstream>
#include <conio.h>
using namespace std;
struct PRICE
{
int number;
char name[20];
int cost;
int quantity;
} *pm;
int Menu();
void PrintPRICE(PRICE);
void sort_cost(PRICE*, int);
void sort_quantity(PRICE*, int);
long file_size(const char*);
int main()
{
int count = 0;
const char *fname = "D:\8.dat";
FILE* file = fopen(fname, "r");
if (file != NULL)
{
long size = file_size(fname);
count = size / sizeof PRICE;
pm = new PRICE[count];
fread(pm, sizeof PRICE, count, file);
fclose(file);
}
for (int i=0; i<count; i++)
{
PrintPRICE(pm[i]);
cout << endl;
}
int ch = Menu();
switch (ch)
{
case 1:
{
sort_cost(pm, count);
cout << endl;
cout << " Result: " << endl;
cout << "-----------------------" << endl;
for (int i=0; i<count; i++)
{
PrintPRICE(pm[i]);
cout << endl;
}
break;
}
case 2:
{
sort_quantity(pm, count);
cout << " Result: " << endl;
cout << "-----------------------" << endl;
for (int i=0; i<count; i++)
{
PrintPRICE(pm[i]);
cout << endl;
}
break;
}
default: break;
}
delete [] pm;
_getch();
}
void PrintPRICE(PRICE price)
{
cout << " Product: " << price.name << endl;
cout << " Number of orden: " << price.number << endl;
cout << " Product cost: " << price.cost << endl;
cout << " Quantity in stock: " << price.quantity << endl;
cout << "-----------------------------------n" << endl;
}
long file_size(const char* filename)
{
FILE *Pfile = NULL;
Pfile = fopen(filename, "rb");
fseek(Pfile, 0, SEEK_END);
long size = ftell(Pfile);
fclose(Pfile);
return size;
}
void sort_cost(PRICE* array, int count)
{
int change = 0;
int comparesion = 0;
for (int i=1; i<count; i++)
{
PRICE key = array[i];
int j = i - 1;
comparesion++;
while (i>=0 && array[i].cost>key.cost)
{
array[j + 1] = array[j];
j = j - 1;
change++;
}
array[j + 1] = key;
}
cout << "n Quantity change: " << change << endl;
cout << " Quantity comparesion: " << comparesion << endl;
}
void sort_quantity(PRICE* array, int count)
{
int change = 0;
int comparesion = 0;
for (int i=1; i<count; i++)
{
PRICE key = array[i];
int j = i - 1;
comparesion++;
while (j>=0 && array[i].quantity>key.quantity)
{
array[j + 1] = array[j];
j = j - 1;
change++;
}
array[j + 1] = array[j];
}
cout << "n Quantity change: " << change << endl;
cout << " Quantity comparesion: " << comparesion << endl;
}
int Menu()
{
int n;
cout << " 1 - Sort by cost" << endl;
cout << " 2 - Sort by quantity" << endl;
cout << "n Your choice: "; cin >> n;
return n;
}

Answer 1

source code for the selection sort
void selectSort(int arr[], int n)
{
int pos_min,temp;
for (int i=0; i < n-1; i++)
{
pos_min = i;
for (int j=i+1; j < n; j++)
{
if (arr[j] < arr[pos_min])
pos_min=j;
}
if (pos_min != i)
{
temp = arr[i];
arr[i] = arr[pos_min];
arr[pos_min] = temp;
}
}
}