题目描述
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You are given a positive integer $K$ and a sequence $A_{1}, A_{2}, \ldots, A_{N}$. Initially, each element of this sequence is $0$ or $1$; your goal is to make all elements equal to $0$.
In order to do that, you may perform the following operation any number of times:
Choose a subarray (a contiguous subsequence) with length $K$, i.e. choose two indices $L$ and $R$ such that $1 ≤ L ≤ R ≤ N$ and $R-L+1 = K$.
Choose one element of that subarray and change it to $0$, i.e. choose an index $P$ such that $L ≤ P ≤ R$ and change $A_{P}$ to $0$.
The cost of this operation is the sum of this subarray $A_{L} + A_{L+1} + \ldots + A_{R}$ before $A_{P}$ is changed.
Find the minimum total cost (sum of costs of individual operations) of making all elements of $A$ equal to $0$.
------ Input ------
The first line of the input contains a single integer $T$ denoting the number of test cases. The description of $T$ test cases follows.
The first line of each test case contains two space-separated integers $N$ and $K$.
The second line contains $N$ space-separated integers $A_{1}, A_{2}, \ldots, A_{N}$.
------ Output ------
For each test case, print a single line containing one integer ― the minimum cost of turning all elements of $A$ into zeros.
------ Constraints ------
$1 ≤ T ≤ 200$
$1 ≤ K ≤ N ≤ 2 \cdot 10^{5}$
$0 ≤ A_{i} ≤ 1$ for each valid $i$
the sum of $N$ over all test cases does not exceed $4 \cdot 10^{5}$
----- Sample Input 1 ------
3
5 3
1 0 1 0 1
4 4
1 1 0 1
3 1
1 1 0
----- Sample Output 1 ------
3
6
2
----- explanation 1 ------
Example case 1: The minimum cost is $3$ and it can be obtained using the following sequence of operations:
- choose the subarray $[L,R] = [2,4]$ and set $A_{3}=0$ with cost $1$
- choose the subarray $[1,3]$ and set $A_{1}=0$ with cost $1$
- choose the subarray $[3,5]$ and set $A_{5}=0$ with cost $1$
Example case 2: We have to choose the whole sequence ($[L,R] = [1,4]$) in each operation, so the total cost is $3+2+1=6$:
- choose the subarray $[1,4]$ and set $A_{1}=0$ with cost $3$
- choose the subarray $[1,4]$ and set $A_{2}=0$ with cost $2$
- choose the subarray $[1,4]$ and set $A_{4}=0$ with cost $1$
Example case 3: The minimum cost is $2$ and it can be obtained using the following sequence of operations:
- choose the subarray $[2,2]$ and set $A_{2}=0$ with cost $1$
- choose the subarray $[1,1]$ and set $A_{1}=0$ with cost $1$
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