单点时限: 1.0 sec
内存限制: 512 MB
You have an empty sequence, and you will be given N queries. Each query is one of these three types:
1 x -Push the element x into the stack.
2 -Delete the element present at the top of the stack.
3 -Print the maximum element in the stack.
The first line of input contains an integer, $N$. The next $N$ lines each contain an above mentioned query. (It is guaranteed that each query is valid.)
$1 \leq N \leq 10^6$
$1 \leq x \leq 10^9 $
$1 \leq type \leq 3 $
For each type 3 query, print the maximum element in the stack on a new line.
10 1 97 2 1 20 2 1 26 1 20 2 3 1 91 3
26 91
对于所有操作复杂度要求$O(1)$或者$O(log(N))$