C++ exercises: selection sort, bubble sort, insertion sort

Q: Consider the record declaration
   struct Month { char name[10]; //name of a month
     int monthnum; //number of days in the month
   };

a) Write a function
   void SortByName(Month months[], int n);
that sorts an array whose elements are of type month by comparing names (use C++ function strcmp). Also write a function
   void SortbyDays(Month months[], int n);
that sorts the list by comparing the number of days in a month. Write a main program that declares an array containing all the months of the year and sorts it using both functions. Print each sorted list.
b) Note that sorting a list of months by number of days produces ties. When this happens a sorting method can use a secondary key to break ties. Write the function
   void Sort2byDays(Month months[], int n);
that sorts the list by first comparing the number of days and, if a tie occurs, breaks the tie by comparing names. Use the function in a main program to print out an ordered list of all the months in the year, ordered by number of days.

#include <iostream>
 
using namespace std;
 
struct Month {
   char name[10];
   int monthnum;
};
 
// Selection sort.
void SortByName(Month month[], int n)
{
   if (n < 2)
      return;
 
   Month hold;
   int min_idx;
   for (int i = 0; i < n - 1; i++)
   {
      hold = month[i];  // selected one to be exchanged with the min.
      min_idx = i;
      for (int j = i + 1; j < n; j++)
      {
         if (strcmp(month[i].name, month[j].name) > 0)
         {
            // Find the min one.
            // Put to the first pos (index of i).
            month[i] = month[j];
            min_idx = j;
         }
      }
 
      if (i != min_idx)
         month[min_idx] = hold;
   }
}
 
// Bubble sort.
void SortByDays(Month month[], int n)
{
   if (n < 2)
      return;
 
   bool changed;
   for (int i = n - 1; i >= 0; i--)
   {
      changed = false;
      for (int j = 0; j < i; j++)
      {
         if (month[j].monthnum > month[j+1].monthnum)
         {
            Month tmpmon;
            tmpmon = month[j];
            month[j] = month[j+1];
            month[j+1] = tmpmon;
 
            changed = true;
         }
      }
      if (!changed)
         break;
   }
}
 
// overload operator < for Month
bool operator<(const Month& mon1, const Month& mon2)
{
   if (mon1.monthnum < mon2.monthnum)
      return true;
   else if (mon1.monthnum > mon2.monthnum)
      return false;
 
   // monthnum equal
   if (strcmp(mon1.name, mon2.name) < 0)
      return true;
   else
      return false;
}
 
// Insertion sort
void Sort2ByDays(Month month[], int n)
{
   Month hold;
 
   for (int i = 1; i < n; i++)
   {
      hold = month[i];  // the one to be inserted.
 
      int j;
      for (j = i; j > 0; j--)
      {
         if (hold < month[j-1])
            month[j] = month[j-1]; // shift right. j-1 is reserved for "hold"
         else
            break;
      }
      month[j] = hold;  // j is the position for what we selected.
   }
}
 
 
void PrintMonths(Month month[], int n)
{
   for (int i = 0; i < n; i++)
   {
      cout << month[i].name << " " << month[i].monthnum << endl;
   }
   cout << endl;
}
 
int main()
{
   const Month months[12] = {
      {"January", 31},
      {"February", 28},
      {"March", 31},
      {"April", 30},
      {"May", 31},
      {"June", 30},
      {"July", 31},
      {"August", 31},
      {"September", 30},
      {"October", 31},
      {"November", 30},
      {"December", 31}
   };

   Month mn[12];

   cout << "--- Original ---" << endl;
   memcpy(mn, months, sizeof(mn));
   PrintMonths(mn, 12);

   cout << "--- SortByName ---" << endl;
   memcpy(mn, months, sizeof(mn));
   SortByName(mn, 12);
   PrintMonths(mn, 12);

   cout << "--- SortByDays ---" << endl;
   memcpy(mn, months, sizeof(mn));
   SortByDays(mn, 12);
   PrintMonths(mn, 12);

   cout << "--- Sort2ByDays ---" << endl;
   memcpy(mn, months, sizeof(mn));
   Sort2ByDays(mn, 12);
   PrintMonths(mn, 12);

   return 0;
}