Question

// Calculate the quarters of a set of integers

#include <iostream>
#include <vector>
#include <algorithm>
#include <conio.h>

using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::sort;

int main()
{
 // Ask for a set of integers
 cout << "Please input a set of integers: "
   << endl;

 // Read the set of integers
  // x is the variable to write
 int x;
  // int_set is the set of integers to write
 vector<int> int_set;
 while (cin >> x)
  {
   int_set.push_back(x);
  }

 // Check if the integer set is vacant 
 typedef std::vector<int>::size_type vec_sz;
 vec_sz size = int_set.size();
 if (size == 0)
  cout << "There are no data. "
    << "Please try again. ";

 // Sort
 sort (int_set.begin(), int_set.end());

 // The set of integers multiply 1/4
 vector<double> int_set_quarter;
 cout << "The quarters of the set of integers are: ";
 for (int i = 0; i != size; ++i)
  {
   int_set_quarter[i] = 1/4 * int_set[i];
   cout << int_set_quarter[i]; 
   cout << endl;
  }

    getch();
 return 0;
}

If you run, then it will collapse…

Answer 1

int_set_quarter‘s size is 0 and you index on it.
Change

vector<double> int_set_quarter;

to

vector<double> int_set_quarter(size);