add new solutions

solutions/9/q918/solution.go

@@ -0,0 +1,22 @@
+package q918
+
+func maxSubarraySumCircular(nums []int) int {
+	maxSum, minSum, maxPfx, minPfx := nums[0], nums[0], 0, 0
+
+	sum := 0
+	for _, num := range nums {
+		sum += num
+		maxSum = max(maxSum, sum-minPfx)
+		minSum = min(minSum, sum-maxPfx)
+
+		maxPfx = max(maxPfx, sum)
+		minPfx = min(minPfx, sum)
+	}
+
+	if sum == minSum {
+		return maxSum
+	}
+	return max(maxSum, sum-minSum)
+}
+
+var _ = maxSubarraySumCircular