Problem: http://www.spoj.com/problems/QTREE/

My solution: http://pastebin.com/pbF0J9Vz http://ideone.com/wtg852

For some reason my code for this problem works on ideone and my local computer but segfaults on SPOJ's judging servers. I tried putting asserts and returns throughout my code to binary search the line of error, which turned out to be line 209, which contains a pointer dereference and comparison that I'm pretty sure is valid. Can anyone help?