Given an integer array arr and an integer k, modify the array
by repeating it k times.
For example, if arr = [1, 2] and k = 3 then the modified array
will be [1, 2, 1, 2, 1, 2].
Return the maximum sub-array sum in the modified array. Note that the length of the sub-array
can be 0 and its sum in that case is 0.
As the answer can be very large, return the answer modulo 10^9
+ 7.
Example 1:
Input: arr = [1,2], k = 3 Output: 9
Example 2:
Input: arr = [1,-2,1], k = 5 Output: 2
Example 3:
Input: arr = [-1,-2], k = 7 Output: 0
Constraints:
1 <= arr.length <= 10^51 <= k <= 10^5-10^4 <= arr[i] <= 10^4