Thread: Incrementing minutes for 12hour time?

Hello I am trying to take input from user for a given 12 hour clock time, then ask how many minutes to add to it, then print increments of each minute until the sum of those minutes is reached. I am having trouble with incrementing to the neccessary hour. Any ideas?

Code:

#include <stdio.h>
main()
{
        int addtime,stophr,stopmin,hr=12,min=0;




        printf("How many minutes do you want to add?");
        scanf("%d",&addtime);
        stophr=(min + addtime/60) + hr;
        stopmin=(min + addtime)%60;
        if(stophr>12)
        {
        stophr=stophr-12;
        }
        if(stopmin>59)
        {
        stopmin=stopmin-60;
        }
        printf("%d:%.02d\n",hr,min);
        while(hr!=stophr && min!=stopmin)
        {
                min++;
        if(hr>12)
        {
        hr=hr-12;
        }
        if(min>59)
        {
        hr=hr+1;
        min=0;
        }


        printf("%d:%.02d\n",hr,min);
        }


        printf("%d:%.02d\n",stophr,stopmin);
}

First, you should make sure your code is neatly formatted and indented (i.e. all code within brackets should be indented one level):

Code:

#include <stdio.h>

int main(void)  /* corrected main() header */
{
    int addtime,stophr,stopmin,hr=12,min=0;

    printf("How many minutes do you want to add?");
    scanf("%d",&addtime);

    stophr=(min + addtime/60) + hr;
    stopmin=(min + addtime)%60;

    if(stophr>12)
    {
        stophr=stophr-12;
    }
    if(stopmin>59)
    {
        stopmin=stopmin-60;
    }

    printf("%d:%.02d\n",hr,min);

    while(hr!=stophr && min!=stopmin)
    {
        min++;

        if(hr>12)
        {
            hr=hr-12;
        }
        if(min>59)
        {
            hr=hr+1;
            min=0;
        }

         printf("%d:%.02d\n",hr,min);
    }

    printf("%d:%.02d\n",stophr,stopmin);
}

The problem lies in your loop condition:

Code:

while(hr!=stophr && min!=stopmin)

For example, if we enter 70, then "stopmin" is set to 10. Once "min" reaches 10 the first time, the loop condition fails.

Instead of looking for the "stop hour" and "stop minute", you might consider controlling your loop with a simple counter that counts up to the maximum number of minutes.

How would one code that?

Originally Posted by Warcom

I get that it would be better to not have stophr and stopmin. But I guess I don't know how to increment the time to the required stop time.
Say 300 minutes are the addtime what Boolean would I use to loop the increment ?

You don't even need the "stop time". The body of the loop should just continue incrementing hours/minutes, while the loop condition should be controlled by a separate (counter) variable.

If you've learned about for() loops, this would be a perfect application to use one.

Thank you Matticus,
I was thinking about a for loop but I was wondering how to set it to only increment the number of added minutes.
say the number is 300 can I go
for (min<addtime; min++) ?

Originally Posted by Warcom

Thank you Matticus,
I was thinking about a for loop but I was wondering how to set it to only increment the number of added minutes.
say the number is 300 can I go
for (min<addtime; min++) ?

Yes, you are on the right track, since "addtime" contains the total number of minutes. Be sure to use a separate variable for the counter, as "min" is used for other purposes.

Originally Posted by Warcom

Hello I am trying to take input from user for a given 12 hour clock time, then ask how many minutes to add to it, then print increments of each minute until the sum of those minutes is reached. I am having trouble with incrementing to the neccessary hour. Any ideas?

Code:

#include <stdio.h>
main()
{
        int addtime,stophr,stopmin,hr=12,min=0;




        printf("How many minutes do you want to add?");
        scanf("%d",&addtime);
        stophr=(min + addtime/60) + hr;
        stopmin=(min + addtime)%60;
        if(stophr>12)
        {
        stophr=stophr-12;
        }
        if(stopmin>59)
        {
        stopmin=stopmin-60;
        }
        printf("%d:%.02d\n",hr,min);
        while(hr!=stophr && min!=stopmin)
        {
                min++;
        if(hr>12)
        {
        hr=hr-12;
        }
        if(min>59)
        {
        hr=hr+1;
        min=0;
        }


        printf("%d:%.02d\n",hr,min);
        }


        printf("%d:%.02d\n",stophr,stopmin);
}

The part that is giving me the trouble is how to get the increments of minutes to stop at the added time. printf("%d:%.02d\n",hr,min);

while(hr!=stophr && min!=stopmin)

the output will print the right start time but won't increment all the way to the stop time.

I get that it would be better to not have stophr and stopmin. But I guess I don't know how to increment the time to the required stop time.
Say 300 minutes are the addtime what Boolean would I use to loop the increment ?

You need another variable to act as a counter.
You need a loop condition that checks this counter value against the total number of minutes that need to be counted.

Expressing logic via code is a learned skill, so spend a little time mulling it over, then attempt to implement it yourself. If you get stuck, post your updated code along with specific questions, and we can go from there.

To determine the correct while condition think about when you want it to stop. You want it to stop when hr==stophr && min==stopmin, therefore you want it to continue while (!(hr==stophr && min==stopmin)), or (by deMorgan's laws), while (hr != stophr || min != stopmin).

However, this won't work for addtime greater than or equal to 12 * 60. So it would be better to just use a counter as Matticus said.

That worked perfect for the hr change. Do you have any hints for me as to why the P will switch to A but the A will not switch to P?

Originally Posted by algorism

Also note that you're wrapping hr in the wrong place (before you increment it!). It should be something like:

Code:

        if (++min > 59) {
            min = 0;
            if (++hr > 12)
                hr = 1;
        }

Originally Posted by algorism

Again, it's a matter of the relative position of the code. Instead of testing if hr is 1 (which it will be over and over again from 1:00 to 1:59), put the am/pm code in where hr is set to 1.

Code:

if (++min > 59) {
    min = 0;
    if (++hr > 12) {
        hr = 1;
        // put the am/pm code in here (but don't bother checking for hr == 1 since we already know that)
    }
}

EDIT: Actually, now that I think about it that's not quite right. It's more like:

Code:

if (++min > 59) {
    min = 0;
    if (++hr == 12) {
        // put the am/pm code in here
    }
    else if (hr > 12)
        hr = 1;
}

I added what you suggested previously and my only remaining problem was the AM not switching to PM

But now not even the minutes are incrementing properly

Any idea where I went wrong?

Code:

    for(i=0;i<addtime;i++)
                        {
                        if (++min > 59)
                         {
                        min = 0;
                         }
                        if (++hr == 12 && ampm=='P')
                                {
                                ampm='A';
                                }
                                if (++hr == 12 && ampm=='A')
                                        {
                                ampm='P';
                                }
                                else if(hr>12)
                                {
                                hr=1;
                                }




         printf("%d:%.02d %cM\n",hr,min,ampm);

Or simply:

Code:

while (addtime-- > 0) {
    ...
}