Shortest Unsorted Continuous Subarray

class Solution:
    def findUnsortedSubarray(self, nums: List[int]) -> int:
        n = len(nums)

        preMax = float("-inf")
        sufMin = float("+inf")

        st = 0
        en = -1

        for i in range(n):
            preMax = max(preMax, nums[i])
            if preMax != nums[i]:
                en = i

        for i in range(n-1, -1, -1):
            sufMin = min(sufMin, nums[i])
            if sufMin != nums[i]:
                st = i

        return en-st+1