qsort(3)

1. Read the manpage of qsort().
2. Modify the following code by replacing your own sort_array() with the qsort() provided by standard C library (<cstdlib>).
3. You need to design a function cmpFunc() so that the following code can sort an array of integers.

   
   // Pointer to Function
   #include <iostream>
   
   int f1(int n) { return -n; }
   int f2(int n) { return (n % 10) + (n / 10); }
   int f3(int n) { return n; }
   
   void sort_array(int a[], int n, int (*f)(int)) {
       int temp;
       for (int i=0; i<n-1; ++i)
           for (int j=i+1; j<n; ++j)
               if (f(a[i]) > f(a[j]))
               {
                   temp = a[i]; a[i] = a[j]; a[j] = temp;
               }
   }
   
   void print_array(int a[], int n) {
       for (int i=0; i<n; ++i)
           std::cout << a[i] << (i==n-1?'\n':' ');
   }
   
   int main()
   {
       int (*pfun[3])(int) = { f1, f2, f3 };
       int a[10] = { 57, 33, 18, 21, 70, 67, 44, 41, 82, 92 };
       for (int i=0; i<3; ++i) {
           sort_array(a, 10, pfun[i]);
           print_array(a, 10);
       }
       return 0;
   }