First of all, we wanted to check if regular expressions work well. We made some test cases for regular expressions to check if they work well. However, when we ran test cases, it kept printing segmentation fault. So we put print messages through regular expressions and change the regular expressions if the message is not printed. After changing them, at least they works well. Before we didn't know about regular expressions problem, we spent about 8 hours to find where the segmentation fault occurs.
After we fixed this problem, some of the test cases went to infinite loop. The problem of that part was hard to find and fix.
Working in pairs was very efficient. It is better for other person to look at a programmer's code to find an error what he misses. It happens when we work together for iteration1.
The most wasting time part was debugging when we worked on iteration1.