A16244 · Make It Zero

题目描述

During Zhongkao examination, Reycloer met an interesting problem, but he cannot come up with a solution immediately. Time is running out! Please help him. Initially, you are given an array $a$ consisting of $n \ge 2$ integers, and you want to change all elements in it to $0$ . In one operation, you select two indices $l$ and $r$ ( $1\le l\le r\le n$ ) and do the following: - Let $s=a_l\oplus a_{l+1}\oplus \ldots \oplus a_r$ , where $\oplus$ denotes the [bitwise XOR operation](https://en.wikipedia.org/wiki/Bitwise_operation#XOR); - Then, for all $l\le i\le r$ , replace $a_i$ with $s$ . You can use the operation above in any order at most $8$ times in total. Find a sequence of operations, such that after performing the operations in order, all elements in $a$ are equal to $0$ . It can be proven that the solution always exists.

The first line of input contains a single integer $t$ ( $1\le t\le 500$ ) — the number of test cases. The description of test cases follows. The first line of each test case contains a single integer $n$ ( $2\le n\le 100$ ) — the length of the array $a$ . The second line of each test case contains $n$ integers $a_1,a_2,\ldots,a_n$ ( $0\le a_i\le 100$ ) — the elements of the array $a$ .

For each test case, in the first line output a single integer $k$ ( $0\le k\le 8$ ) — the number of operations you use. Then print $k$ lines, in the $i$ -th line output two integers $l_i$ and $r_i$ ( $1\le l_i\le r_i\le n$ ) representing that you select $l_i$ and $r_i$ in the $i$ -th operation. Note that you do not have to minimize $k$ . If there are multiple solutions, you may output any of them.

输入 #1

6
4
1 2 3 0
8
3 1 4 1 5 9 2 6
6
1 5 4 1 4 7
5
0 0 0 0 0
7
1 1 9 9 0 1 8
3
100 100 0

输出 #1