Adding time in format hh:mm in C++

Question

How can I do it in C++?

Example:

time1 = 04:45; 
time2 = 02:25; 
result = time1 + time2;
result = 07:10

In which date type (string, double, etc) should time values be saved?

edit: Is it possible from this code get int h = 23 and int m = 14? In other words, how to print %H and %M?

int main()
{
    std::tm t = {};
    std::istringstream ss("23:12");
    ss >> std::get_time(&t, "%H:%M");
    if (ss.fail()) {
        std::cout << "Parse failed\n";
    } else {
        std::cout << std::put_time(&t, "%R") << '\n';
    }
}

We're not here to write code for you. What have you tried? Show your work! Then ask *specific* questions. — Hermann Döppes, Dec 09 '16 at 17:19
Look here for parsing: http://en.cppreference.com/w/cpp/io/manip/get_time — Felix Glas, Dec 09 '16 at 17:21
Did you think a few minutes of how would you add such times "by hand" (more precisely by yourself, without computers), with pencil and paper? — Basile Starynkevitch, Dec 09 '16 at 17:47
And what about the minutes? How do you handle them on paper? — Basile Starynkevitch, Dec 09 '16 at 17:53
@BasileStarynkevitch 1) I would add hours. 4+2 =6 2) add minutes 45+25 = 70 3) 70/60 = 1 add 1 to 6 = 7. 4) 70%60 =10 7 hours 10 minutes or 7.16666 hours — Busspotter Penguin, Dec 09 '16 at 17:54
That is why I ask here because I don't know it... I have 04:45 in one string. You think I should do something like "before : are hours and after it minutes?" — Busspotter Penguin, Dec 09 '16 at 18:05
@BasileStarynkevitch Please look in edit, there I have new specific question. — Busspotter Penguin, Dec 09 '16 at 20:59
You should read the documentation (my answer gave a lot of references), try something, and if needed (but you should be able to find out by yourself) ask another question. Your edit is not related to the original question. But before asking, be sure to take several hours to read documentation and try things. — Basile Starynkevitch, Dec 10 '16 at 07:45
When asking a new question, cite the references you have read and give the code that you have tried and explain what you have understood. Be sure to compile with all warnings (improve your code till you get none) and to use the debugger. — Basile Starynkevitch, Dec 10 '16 at 07:50
@HermannDöppes Meine Arbeit - dank Link von snps und Hilfe des freundes. Imho das ist besser. — Busspotter Penguin, Dec 10 '16 at 14:48

score 2 · Answer 1 · edited May 23 '17 at 12:13

Look into the <chrono> standard C++11 header. See also this question.

You would convert the "04:25" string (read a lot more about std::string, which has a quite rich API) to some time (actually, a time_point, or a clock, or a duration) and work on that time.

On POSIX systems (notably Linux) you might instead use (even with an old C++ or in plain C) the time related functions (read time(7)...) such as strftime(3) and strptime(3) (see also localtime(3) & timelocal(3)...)

Alternatively, you might simply compute minutes, with the insight that "04:45" should be parsed as 04 (in decimal, use std::stoi to convert, or even the strtol function of C or its sscanf) * 60 + 45 and "07:10" is 7*60 +10 that is 430; to make the reverse transformation consider 430/60 (giving 7) and 430%60 giving 10.

Don't forget to enable all warnings & debug info when compiling (e.g. compile with g++ -Wall -Wextra -g if using GCC...) and use the debugger (e.g.gdb) to understand the behavior of your program (e.g. by running it step by step and querying its state).

Your question is extremely basic (and shows some difficulty with elementary programming and math, unrelated to C++). I strongly recommend spending days in reading some basic math textbook (high-school level, explaining quotient and modulus and bases & radixes), then SICP (an excellent introduction to programming, not using C++), then Programming using C++. Don't forget to read some reference documentation about C++.

score 0 · Answer 2 · answered Dec 11 '16 at 18:46

(Posted solution on behalf of OP).

My work - it works! (inspired by snps's link and friend's help) link

int convert_time_to_minutes(string sss)
{

    istringstream ss(sss);
    string hh,mm;
    getline(ss, hh,':');
    getline(ss, mm,';');


    double h,m; //hours, minutes
    h = atoi(hh.c_str());
    m = atoi(mm.c_str());
    double minutes = (h *60 + m)/60;
    cout << minutes;
    return minutes;

}

Use this function twice for two times, than add two return values and I have result in minutes.

Adding time in format hh:mm in C++

2 Answers2