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问题 K: Dynamic Arrays and List - Deque

内存限制:512 MB 时间限制:2 S 标准输入输出
题目类型:传统 评测方式:文本比较

题目描述

Deque 

For a dynamic array A={a0,a1,...} of integers, perform a sequence of the following operations: 

0 push(d, x): Add element x at the begining of A, if d=0. Add element x at the end of A, if d=1. 

1 randomAccess(p): Print element ap. 

2 pop(d): Delete the first element of A, if d=0. Delete the last element of A, if d=1. A is a 0-origin array and it is empty in the initial state.

输入格式

The input is given in the following format.

q

query1

query2

:

queryq

Each query queryi is given by 0 d x , or 1 p, or 2 d ,where the first digits 0, 1 and 2 represent push, randomAccess and pop operations respectively. randomAccess and pop operations will not be given for an empty array. 1≤q≤400,000 0≤p< the size of A −1,000,000,000≤x≤1,000,000,000

输出格式

For each randomAccess, print ap in a line.

输入样例 复制

11
0 0 1
0 0 2
0 1 3
1 0
1 1
1 2
2 0
2 1
0 0 4
1 0
1 1

输出样例 复制

2
1
3
4
1