#P6960. [NEERC2017] Interactive Sort

[NEERC2017] Interactive Sort

题目背景

这是一道 IO 交互题。

题目描述

Ivan wants to play a game with you. He took all integers from 11 to nn inclusive, shuffled them and then put all even numbers into array ee and all odd numbers into array oo .

Your task is to find arrays ee and oo .

You can ask Ivan questions of certain kind. Each question consists of two integers ii and jj . For each question Ivan says whether e[i]<o[j]e[i] < o[j] or not.

You can ask at most 300000300 000 questions.

Interaction Protocol

First, the testing system writes the integer n(1n10000)n (1 \le n \le 10 000) -- the number of integers Ivan used.

Your solution shall print requests of two types:

• “? i j”. 1in/2,1jn/21 \le i \le ⌊n/2⌋, 1 \le j \le ⌈n/2⌉. The testing system responds with the symbol <“<” if e[i]<o[j]e[i] < o[j] or with the symbol >“>” otherwise.

• “!\ $e_1\ e_2\ \cdots e_{⌊n/2⌋}\ o_1\ o_2 \cdots o_{⌈n/2⌉}$” tells the values of ee and oo that your program has determined.

Don't forget to flush the output after each request!

Your solution must issue exactly one request of the second type, which must be the last request, and thesolution must terminate gracefully after issuing it.

Your solution is allowed to issue at most 300000300 000 requests of the first type.

For each test case the number nn is fixed and the numbers are shuffled using Java built-in shuffle functionwith fixed seed.

题目大意

有一个长度为 n(n10000)n(n\le 10000) 的排列,所有奇数组成的序列设为 oo,所有偶数组成的序列设为 ee

你可以进行不超过 300000300000 次询问 ? i j,每次交互库会返回一个 <> 表示 eie_iojo_j 的大小关系,最后你需要求出 e,oe,o 并输出,格式为 ! e o

保证数据随机。

5
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? 1 1
? 1 2
? 1 3
? 2 1
? 2 2
? 2 3
! 4 2 1 3 5