difference_of_two_times_in_minutes_v1.c

/*

    difference_of_two_times_in_minutes_v1.c

    Task from Choo Yong Han :
    https://web.facebook.com/albertchooyonghan
    https://web.facebook.com/photo.php?fbid=3902250669845726&set=pcb.1588682431290601&type=3&theater&ifg=1

    1030 - 0830 = 120 minutes

I see that you succeed to read data (numbers) to matrix,
but difference of time is wrong.

Example:

1030 - 0830

You have to extract first two digits, make number of them,
multiply that number (represent hours) by 60 minutes and
add to it minutes made of third and fourth digit.

10*60+30 - 8*60+30 = 120 minutes

Then convert 120 minutes to hours and minutes.

120 = 120/60 + 120%60

First / is integer division,
second is rest (reminder) of division.

So,

120 minutes is 2 hours and 0 minutes.

At last, if needed, convert that to
0200.

This will work if both times are from same day.


Here is a better solution using structures with integers:
https://www.includehelp.com/code-snippets/print-difference-of-two-times-in-hours-minutes-and-seconds-in-c-language.aspx
https://www.programiz.com/c-programming/examples/time-structure


    You can find all my C programs at Dragan Milicev's pastebin:

    https://pastebin.com/u/dmilicev

*/

#include <stdio.h>
#include <stdlib.h>     // for atoi()


// Returns difference end_time - start_time in minutes
int difference_of_two_times_in_minutes( char start_time[], char end_time[] )
{
    char str_h_end_time[3], str_m_end_time[3], str_h_start_time[3], str_m_start_time[3];    // time strings
    int time2_hours, time2_minutes, time1_hours, time1_minutes;     // time integers
    int difference_in_minutes;

    str_h_end_time[0] = end_time[0];
    str_h_end_time[1] = end_time[1];
    str_h_end_time[2] = '\0';               // finish the string
    time2_hours = atoi(str_h_end_time);

    str_m_end_time[0] = end_time[2];
    str_m_end_time[1] = end_time[3];
    str_m_end_time[2] = '\0';               // finish the string
    time2_minutes = atoi(str_m_end_time);

    str_h_start_time[0] = start_time[0];
    str_h_start_time[1] = start_time[1];
    str_h_start_time[2] = '\0';             // finish the string
    time1_hours = atoi(str_h_start_time);

    str_m_start_time[0] = start_time[2];
    str_m_start_time[1] = start_time[3];
    str_m_start_time[2] = '\0';             // finish the string
    time1_minutes = atoi(str_m_start_time);

    difference_in_minutes = (time2_hours - time1_hours)*60 + (time2_minutes - time1_minutes);
    return(difference_in_minutes);
}


int main(void)
{
    char end_time[]   = "1030";
    char start_time[] = "0830";
    int difference_in_minutes, h, m;

    difference_in_minutes = difference_of_two_times_in_minutes(start_time, end_time);

    printf("\n The difference %s - %s in minutes is %d minutes. \n",
            end_time, start_time, difference_in_minutes);

    h = difference_in_minutes / 60;
    m = difference_in_minutes % 60;

    printf("\n %d minutes is %d hours and %d minutes. \n", difference_in_minutes, h, m);

    printf("\n %d minutes is ", difference_in_minutes);

    if( h < 10 )
        printf("0%d:", h);
    else
        printf("%2d:", h);

    if( m < 10 )
        printf("0%d h \n", m);
    else
        printf("%2d h \n", m);


    return 0;

} // main()