Sequence and Swaps

题意翻译

给出一个序列和 $x$，每次可以把序列中的一个 $> x$ 的数与 $x$ 交换，问最少操作多少次使得整个序列升序排序，如果不能输出 `-1`。

题目描述

You are given a sequence $ a $ consisting of $ n $ integers $ a_1, a_2, \dots, a_n $ , and an integer $ x $ . Your task is to make the sequence $ a $ sorted (it is considered sorted if the condition $ a_1 \le a_2 \le a_3 \le \dots \le a_n $ holds). To make the sequence sorted, you may perform the following operation any number of times you want (possibly zero): choose an integer $ i $ such that $ 1 \le i \le n $ and $ a_i > x $ , and swap the values of $ a_i $ and $ x $ . For example, if $ a = [0, 2, 3, 5, 4] $ , $ x = 1 $ , the following sequence of operations is possible: 1. choose $ i = 2 $ (it is possible since $ a_2 > x $ ), then $ a = [0, 1, 3, 5, 4] $ , $ x = 2 $ ; 2. choose $ i = 3 $ (it is possible since $ a_3 > x $ ), then $ a = [0, 1, 2, 5, 4] $ , $ x = 3 $ ; 3. choose $ i = 4 $ (it is possible since $ a_4 > x $ ), then $ a = [0, 1, 2, 3, 4] $ , $ x = 5 $ . Calculate the minimum number of operations you have to perform so that $ a $ becomes sorted, or report that it is impossible.

输入输出格式

输入格式

The first line contains one integer $ t $ ( $ 1 \le t \le 500 $ ) — the number of test cases. Each test case consists of two lines. The first line contains two integers $ n $ and $ x $ ( $ 1 \le n \le 500 $ , $ 0 \le x \le 500 $ ) — the number of elements in the sequence and the initial value of $ x $ . The second line contains $ n $ integers $ a_1 $ , $ a_2 $ , ..., $ a_n $ ( $ 0 \le a_i \le 500 $ ). The sum of values of $ n $ over all test cases in the input does not exceed $ 500 $ .

输出格式

For each test case, print one integer — the minimum number of operations you have to perform to make $ a $ sorted, or $ -1 $ , if it is impossible.

输入输出样例

输入样例 #1

6
4 1
2 3 5 4
5 6
1 1 3 4 4
1 10
2
2 10
11 9
2 10
12 11
5 18
81 324 218 413 324

输出样例 #1

3
0
0
-1
1
3