918. Maximum Sum Circular Subarray

class Solution {
public:
    int maxSubarraySumCircular(vector<int>& nums) {
        int curMax = 0, curMin = 0;
        int maxSum = nums[0], minSum = nums[0];
        int totalSum = 0;

        for(int num : nums) {
            curMax = max(curMax + num, num);
            maxSum = max(maxSum, curMax);

            curMin = min(curMin + num, num);
            minSum = min(minSum, curMin);

            totalSum += num;
        }
        if(totalSum == minSum) {
            return maxSum;
        }
        return max(maxSum, totalSum - minSum);
    }
};

• T: $O(N)$
• S: $O(1)$