Thread: Formatting string to time

Hi! I have the following problem: I need to make a digital timer. I must have always 4 digits in the format MM:SS. I know the functions width() and fill(), but I do not know how work with them to acchieve what I need.
For example 1 minute and 2 seconds must be shown as: 01:02, and not 1:2, or 1: 2.
Any help would be appreciated.

Read here, attempt to write it yourself, then post your code here when you're stuck.

First, thanks for the help! I have created a solution, altough it is slow:

Code:

      stringstream str;
      str.fill('0');
      str.width(2);
      str << (currentTime-initialTime)/60;
      str << ':';
      str.width(2);
      str << (currentTime-initialTime)%60;
      string str2;
      str >> str2;
      mClock->value(str2.c_str());

Is there any faster way?

How about sticking with cout and avoiding use of stringstreams? Sorry, no compiler handy to test before posting.

#include<iomanip>

cout.setiosflags(ios::right);
cout << setw(2) << setfill('0') <<

or if you (as some others) prefer, using the format string of printf() to accomplish your needs.

or even

if((currentTime-initialTime)/60 < 10)
cout << '0' << (currentTime-initialTime)/60;
else
cout << (currentTime-initialTime)/60;

I already tryied printf, but it does not fill with '0'. I need string stream because I do not want to write to the screen. Your option of using if is good, I thought about it, but didn't realize that could get simpler.

Thanks for the help!

Originally Posted by gustavosserra

I already tryied printf, but it does not fill with '0'. I need string stream because I do not want to write to the screen.

Then you didn't use it correctly, nor dud you use the proper function.

Code:

      stringstream str;
      str.fill('0');
      str.width(2);
      str << (currentTime-initialTime)/60;
      str << ':';
      str.width(2);
      str << (currentTime-initialTime)%60;
      string str2;
      str >> str2;

would become

Code:

sprintf(str, "%02d:%02d", (currentTime-initialTime)/60, (currentTime-initialTime)%60);

Writes to the char buffer str, zero filled.

Thank you so much!!!