Maychallenge (45) | Maximum Sum Circular Subarray

Given a circular array C of integers represented by A, find the maximum possible sum of a non-empty subarray of C.

Here, a circular array means the end of the array connects to the beginning of the array.  (Formally, C[i] = A[i] when 0 <= i < A.length, and C[i+A.length] = C[i] when i >= 0.)

Also, a subarray may only include each element of the fixed buffer A at most once.  (Formally, for a subarray C[i], C[i+1], ..., C[j], there does not exist i <= k1, k2 <= j with k1 % A.length = k2 % A.length.)

Example 1:

Input: [1,-2,3,-2]
Output: 3
Explanation: Subarray [3] has maximum sum 3

Example 2:

Input: [5,-3,5]
Output: 10
Explanation: Subarray [5,5] has maximum sum 5 + 5 = 10

Example 3:

Input: [3,-1,2,-1]
Output: 4
Explanation: Subarray [2,-1,3] has maximum sum 2 + (-1) + 3 = 4

Example 4:

Input: [3,-2,2,-3]
Output: 3
Explanation: Subarray [3] and [3,-2,2] both have maximum sum 3

Example 5:

Input: [-2,-3,-1]
Output: -1
Explanation: Subarray [-1] has maximum sum -1

Note:

1. -30000 <= A[i] <= 30000
2. 1 <= A.length <= 30000

This is a problem separate from two bit problem. If you read the post MaxSequence of me, you can past one case in it. Sumary, that three case:

1. [-2,-3,-1], if all number is negative, result is max number negative.
2. [5,-3,5], if max not in arr, it must be circual arr, result = sum (7) - (-3) (the part not belong result) .
3. [1,-2,3,-2], find max sequence. .

Image from Internet, maximum sum circular subarray.

Case 1 & 3 you can do it, else case 2, we find the part not belong result - is the min part, i convert array A to -A and find max sequence is the min part.

Example [5,-3,-1,5] convert [-5,3,1,-5], max sequence is 4, so  min sequence should be arr raw is -4. Sum = 5 + -3 + -1 + 5 = 6. => Result = 6 - (-4) = 10. That [5......5] in cicular subarray.
This is code me implement by Java:
Thanks you and see you later !