# LC 918. 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`

Runtime: 76 ms, faster than 100.00% of C++ online submissions for Maximum Sum Circular Subarray.
Memory Usage: 13.2 MB, less than 0.77% of C++ online submissions for Maximum Sum Circular Subarray.

```class Solution {
public:
int maxSubarraySumCircular(vector<int>& A) {
int total = 0;
int curmax = 0, maxsum = INT32_MIN;
int curmin = 0, minsum = INT32_MAX;
for(int a : A) {
curmax = max(curmax + a, a);
maxsum = max(maxsum, curmax);
curmin = min(curmin + a, a);
minsum = min(minsum, curmin);
total += a;
}
return maxsum > 0 ? max(maxsum, total - minsum) : maxsum;
}
};```

LC 918. Maximum Sum Circular Subarray

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