Here is my code. I used the technics as described by others, but it still won't work.
//Code deleted.

Edited by author 17.09.2015 12:29

OK, I get that by myself. I've deleted the code I put here before. I implemented a binary heap by myself, and used it to pass the problem. It worked.

Cabbage,can you give me your code?I can't solve this MLE problem.:(.My email is xuantungptit@gmail.com

I got MLE too! But then I used vector and got AC.
Instead of priority_queue try to use vector and algorithms: make_heap, push_heap, pop_heap, sort_heap. In some topic here I saw  detailed information on this solution which helped me to get AC.