918. Maximum Sum Circular Subarray

Bug
One** corner case** to pay attention:
If all number are negative,
return the maximum one,
(which equals to the max subarray sum)

If the maximum sum is negative, means all numbers are negative
In this case, total sum is the minimum one -> total sum - min sum = 0, which is not a valid subarray
So when maxSum < 0, return maxSum

21.88 %
class Solution {
    public int maxSubarraySumCircular(int[] A) {
        // max subarray sum, min suarray sum
        // result = Math.max(max, totalSum - min)
        if (A == null || A.length == 0) return 0;
        int prevMin = A[0], prevMax = A[0]; // min/max subarray sum end with i-1
        int sum = A[0], max = A[0], min = A[0];
        for (int i = 1; i < A.length; i++) {
            sum += A[i];
            int currMin = Math.min(prevMin, 0) + A[i];
            int currMax = Math.max(prevMax, 0) + A[i];
            max = Math.max(max, currMax);
            min = Math.min(min, currMin);
            prevMin = currMin;
            prevMax = currMax;
        }
        return max > 0 ? Math.max(max, sum - min) : max;
    }
}