Array Eversion

题意翻译

给定长度为 $n$ 的序列 $a$。 每次操作取出序列中最后一个元素 $a_n$，记为 $x$。 将 $a$ 中不大于 $x$ 的元素按照在 $a$ 中的顺序放入 $b$ 数组中，大于 $x$ 的元素同样按照在 $a$ 中的顺序放入 $c$ 数组中。 然后将 $c$ 数组拼接到 $b$ 数组的后面，变成新的 $a$ 数组。 求一个最小的整数 $k$，使得进行了 $k$ 次操作后，不论再进行多少次操作，$a$ 数组都不会变化。 $1\le n\le 2\times 10^5$，$1\le a_i \le 10^9$。

题目描述

You are given an array $ a $ of length $ n $ . Let's define the eversion operation. Let $ x = a_n $ . Then array $ a $ is partitioned into two parts: left and right. The left part contains the elements of $ a $ that are not greater than $ x $ ( $ \le x $ ). The right part contains the elements of $ a $ that are strictly greater than $ x $ ( $ > x $ ). The order of elements in each part is kept the same as before the operation, i. e. the partition is stable. Then the array is replaced with the concatenation of the left and the right parts. For example, if the array $ a $ is $ [2, 4, 1, 5, 3] $ , the eversion goes like this: $ [2, 4, 1, 5, 3] \to [2, 1, 3], [4, 5] \to [2, 1, 3, 4, 5] $ . We start with the array $ a $ and perform eversions on this array. We can prove that after several eversions the array $ a $ stops changing. Output the minimum number $ k $ such that the array stops changing after $ k $ eversions.

输入输出格式

输入格式

Each test contains multiple test cases. The first line contains the number of test cases $ t $ ( $ 1 \le t \le 100 $ ). Description of the test cases follows. The first line contains a single integer $ n $ ( $ 1 \le n \le 2 \cdot 10^5 $ ). The second line contains $ n $ integers $ a_1, a_2, \dots, a_n $ ( $ 1 \le a_i \le 10^9 $ ). It is guaranteed that the sum of $ n $ over all test cases does not exceed $ 2 \cdot 10^5 $ .

输出格式

For each test case print a single integer $ k $ — the number of eversions after which the array stops changing.

输入输出样例

输入样例 #1

3
5
2 4 1 5 3
5
5 3 2 4 1
4
1 1 1 1

输出样例 #1

1
2
0

说明

Consider the fist example. - The first eversion: $ a = [1, 4, 2, 5, 3] $ , $ x = 3 $ . $ [2, 4, 1, 5, 3] \to [2, 1, 3], [4, 5] \to [2, 1, 3, 4, 5] $ . - The second and following eversions: $ a = [2, 1, 3, 4, 5] $ , $ x = 5 $ . $ [2, 1, 3, 4, 5] \to [2, 1, 3, 4, 5], [] \to [2, 1, 3, 4, 5] $ . This eversion does not change the array, so the answer is $ 1 $ . Consider the second example. - The first eversion: $ a = [5, 3, 2, 4, 1] $ , $ x = 1 $ . $ [5, 3, 2, 4, 1] \to [1], [5, 3, 2, 4] \to [1, 5, 3, 2, 4] $ . - The second eversion: $ a = [1, 5, 3, 2, 4] $ , $ x = 4 $ . $ [1, 5, 3, 2, 4] \to [1, 3, 2, 4], [5] \to [1, 3, 2, 4, 5] $ . - The third and following eversions: $ a = [1, 3, 2, 4, 5] $ , $ x = 5 $ . $ [1, 3, 2, 4, 5] \to [1, 3, 2, 4, 5], [] \to [1, 3, 2, 4, 5] $ . This eversion does not change the array, so the answer is $ 2 $ .