[Solution] Rising Sand Codeforces Solution

[Solution] Rising Sand Codeforces Solution | Codeforces Problem Solution 2022

B. Rising Sand

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

There are n$n$ piles of sand where the i$i$-th pile has ai$a_i$ blocks of sand. The i$i$-th pile pile is called too tall if 1<i<n$1<i<n$ and ai>ai−1+ai+1$a_i>a_{i-1}+a_{i+1}$. That is, a pile is too tall if it has more sand than its two neighbours combined. (Note that piles on the ends of the array cannot be too tall.)

You are given an integer k$k$. An operation consists of picking k$k$ consecutive piles of sand and adding one unit of sand to them all. Formally, pick 1≤l,r≤n$1\le l,r\le n$ such that r−l+1=k$r-l+1=k$. Then for all l≤i≤r$l\le i\le r$, update ai←ai+1$a_i\leftarrow a_i+1$.

What is the maximum number of piles that can simultaneously be too tall after some (possibly zero) operations?

Input

The input consists of multiple test cases. The first line contains an integer t$t$ (1≤t≤1000$1\le t\le 1000$) — the number of test cases. The description of the test cases follows.

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The first line of each test case contains two integers n$n$ and k$k$ (3≤n≤2⋅105$3\le n\le 2\cdot {10}^5$; 1≤k≤n$1\le k\le n$) — the number of piles of sand and the size of the operation, respectively.

The second line of each test case contains n$n$ integers a1,a2,…,an$a_1,a_2,\dots ,a_n$ (1≤ai≤109$1\le a_i\le {10}^9$) — the sizes of the piles.

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It is guaranteed that the sum of n$n$ over all test cases does not exceed 2⋅105$2\cdot {10}^5$.

Output

For each test case, output a single integer — the maximum number of piles that are simultaneously too tall after some (possibly zero) operations.