// Incomplete version
#include <iostream>
using namespace std;

struct Mytime
{
   int hours;
   int mins;
};

int timecmp(Mytime,Mytime);
// returns 0 if times are same
// returns >0 if first is later than second
// returns <0 if first is before second

int setTime(Mytime& t, int h, int m );
// if valid time sets hh and mm to h and m 
// and returns 0
// if invalid returns integer > 0 as error code
// error code +1 = underflow hours
// error code +2 = overflow hours
// error code +4 = underflow mins
// error code +8 = overflow mins

void display1Time(Mytime t);
// displays in form hh:mm

void elapsed(Mytime t1, Mytime t2, Mytime& duration);
// determines the time duration between t1 and t2
// t1 assumed to be earlier than t2

void main()
{
    Mytime now;
    Mytime then;
    Mytime howlong;
    
    int h,m;
    
    do // validate input
    {
        cout << "Enter start hh mm : ";
        cin >> h >> m ;
    } while (setTime(now,h,m));
    
    do
    {
        cout << "Enter finish hh mm : ";
        cin >> h >> m ;
    } while (setTime(then,h,m));
    
    elapsed(now,then,howlong);

    cout << "Time elapsed from ";
    display1Time(now);
    cout << " until ";
    display1Time(then);
    
    cout << " is ";
    display1Time(howlong);
    cout << endl;
}

int timecmp(Mytime t1,Mytime t2)
{
   if (t1.hours == t2.hours)
   {
      if (t1.mins == t2.mins)
      {
         return 0;
      }
      else // mins not same
      {
         if (t1.mins > t2.mins)
         {
            return 1; // greater than zero
         }
         else
         {
            return -1;
         }
      }
   }
   else // hours not same
   {
      if (t1.mins > t2.mins)
      {
         return 1;
      }
      else
      {
         return -1;
      }
   }
}

int setTime(Mytime& t, int h, int m )
{
    int errorCode = 0;
    if (h < 0) errorCode += 1;
    if (h > 23) errorCode += 2;
    if (m < 0) errorCode += 4;
    if (m > 59) errorCode += 8;
    if (errorCode==0){t.hours = h; t.mins = m;}
    return errorCode;
}

//////////// THE FOLLOWING FUNCTIONS ARE INCOMPLETE

void display1Time(Mytime t)
{
     cout << "00:00";
}


void elapsed(Mytime t1, Mytime t2, Mytime& duration)
{
    setTime(duration,0,0);
}