Codeforces Round 835 (Div. 4) |
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Finished |
You are given an array $$$a[0 \dots n-1]$$$ of $$$n$$$ integers. This array is called a "valley" if there exists exactly one subarray $$$a[l \dots r]$$$ such that:
Here are three examples:
The first image shows the array [$$$3, 2, 2, 1, 2, 2, 3$$$], it is a valley because only subarray with indices $$$l=r=3$$$ satisfies the condition.
The second image shows the array [$$$1, 1, 1, 2, 3, 3, 4, 5, 6, 6, 6$$$], it is a valley because only subarray with indices $$$l=0, r=2$$$ satisfies the codition.
The third image shows the array [$$$1, 2, 3, 4, 3, 2, 1$$$], it is not a valley because two subarrays $$$l=r=0$$$ and $$$l=r=6$$$ that satisfy the condition.
You are asked whether the given array is a valley or not.
Note that we consider the array to be indexed from $$$0$$$.
The first line contains a single integer $$$t$$$ ($$$1 \leq t \leq 10^4$$$) — the number of test cases.
The first line of each test case contains a single integer $$$n$$$ ($$$1 \leq n \leq 2\cdot10^5$$$) — the length of the array.
The second line of each test case contains $$$n$$$ integers $$$a_i$$$ ($$$1 \leq a_i \leq 10^9$$$) — the elements of the array.
It is guaranteed that the sum of $$$n$$$ over all test cases is smaller than $$$2\cdot10^5$$$.
For each test case, output "YES" (without quotes) if the array is a valley, and "NO" (without quotes) otherwise.
You can output the answer in any case (for example, the strings "yEs", "yes", "Yes" and "YES" will be recognized as a positive answer).
673 2 2 1 2 2 3111 1 1 2 3 3 4 5 6 6 671 2 3 4 3 2 179 7 4 6 9 9 101100000000089 4 4 5 9 4 9 10
YES YES NO YES YES NO
The first three test cases are explained in the statement.
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