# CodeChef : January Challenge 2018 – K-Concatenation

By | January 6, 2018

#### K-Concatenation

Source: CodeChef

You are given an array A with size N (indexed from 0) and an integer K. Let’s define another array B with size N · K as the array that’s formed by concatenating K copies of array A.

For example, if A = {1, 2} and K = 3, then B = {1, 2, 1, 2, 1, 2}.

You have to find the maximum subarray sum of the array B. Fomally, you should compute the maximum value of Bi + Bi+1 + Bi+2 + … + Bj, where 0 ≤ i ≤ j < N · K.

### 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 A0, A1, …, AN-1.

### Output

For each test case, print a single line containing the maximum subarray sum of B.

### Constraints

• 1 ≤ T ≤ 10
• 1 ≤ N ≤ 105
• 1 ≤ K ≤ 105
• -106 ≤ Ai ≤ 106 for each valid i

Subtask #1 (18 points): N · K ≤ 105

Subtask #2 (82 points): original constraints

Input:

2
2 3
1 2
3 2
1 -2 1

Output:

9
2

### Explanation

Example case 1: B = {1, 2, 1, 2, 1, 2} and the subarray with maximum sum is the whole {1, 2, 1, 2, 1, 2}. Hence, the answer is 9.

Example case 2: B = {1, -2, 1, 1, -2, 1} and the subarray with maximum sum is {1, 1}. Hence, the answer is 2.

### Solution

Working on the solution.