918. 环形子数组的最大和

https://leetcode-cn.com/problems/maximum-sum-circular-subarray/

参考题解：https://leetcode-cn.com/problems/maximum-sum-circular-subarray/solution/wo-hua-yi-bian-jiu-kan-dong-de-ti-jie-ni-892u/

func maxSubarraySumCircular(nums []int) int {
    total, maxSum, minSum, currMax, currMin := nums[0], nums[0], nums[0], nums[0], nums[0]
    for i := 1; i < len(nums); i++ {
        total += nums[i]
        currMax = max(currMax+nums[i], nums[i])
        maxSum  = max(maxSum, currMax)
        currMin = min(currMin+nums[i], nums[i])
        minSum  = min(minSum, currMin)
    }
    //等价于if maxSum < 0
    if total == minSum  {
        return maxSum
    } else {
        return max(maxSum, total - minSum)
    }
}

func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}

func min(a, b int) int {
    if a < b {
        return a
    }
    return b
}