I use priority queue,the memory that I used is 236 KB,but I still WA at test 5,but I don't know why...

You need use unsigned int.

could someone tell me why ?

Edited by author 18.02.2017 05:40

Edited by author 18.02.2017 05:40

2^31-1 can be stored into signed int.

But, when length of input is even, you need to value average, so (probably) add 2 values and receive integer overflow.
It doesn't mean you must use unsigned. You can avoid overflow in any other way.