Given a circular integer array nums of length n, return the maximum possible sum of a non-empty subarray of nums.

A circular array means the end of the array connects to the beginning of the array. Formally, the next element of nums[i] is nums[(i + 1) % n] and the previous element of nums[i] is nums[(i - 1 + n) % n].

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

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

Solution

/**
 * @param {number[]} nums
 * @return {number}
 */
var maxSubarraySumCircular = function (A) {
  //Declare vars
  let maxSum, max, minSum, min, total;
  //Set initial values
  maxSum = max = minSum = min = total = A[0];

  //Loop through array
  for (let i = 1; i < A.length; i++) {
    //Set n to current value
    const n = A[i];
    //Set max to the max of n or n + max
    max = Math.max(n, n + max);
    //Set maxSum to the max of max or maxSum
    maxSum = Math.max(max, maxSum);
    //Set min to the min of n or n + min
    min = Math.min(n, n + min);
    //Set minSum to the min of min or minSum
    minSum = Math.min(min, minSum);
    //Add n to total
    total += n;
  }
  //Return maxSum if greater than 0, otherwise return maxSum
  return maxSum > 0 ? Math.max(maxSum, total - minSum) : maxSum;
};