Given a sorted integer array nums, where the range of elements are in the inclusive range [lower, upper], return its missing ranges.

Example:

Input:   nums = [0, 1, 3, 50, 75], lower = 0 and upper = 99,
Output: ["2", "4->49", "51->74", "76->99"]

class Solution:
    def findMissingRanges(self, nums, lower: int, upper: int):
        nums.insert(0, lower-1) # Left Bound
        nums.append(upper+1)    # Right Bound
       
        res = []

        for i in range(len(nums)-1):
            left, right = nums[i], nums[i + 1]

            if left != right:
                if right - left == 2:
                    res.append(str(left+1))
                elif right - left > 2:
                    res.append(str(left+1) + "->" + str(right-1))

        return res