I've tried the heap one, I've done everything I could, but still TLE. I guess there should be some tricky part or my implementation error.

what have you guys done to avoid the TLE?

I use heap to arrange the time, everytime there is a new timestamp that is different from the last one, I check the heap and delete the out-of-time nodes.

I also use a bool array to record the existance of a node, as well as a link table to record the next label that can be used. I don't know why I got TLE all the time...