Missing Ranges Meta Version

class Solution {
    public List<String> findMissingRanges(int[] nums, int lower, int upper) {
        List<String> missingRanges = new ArrayList<>();
        int currLower = lower;

        for (int num : nums) {
            if (num > currLower) {
                if (num - currLower > 1) {
                    missingRanges.add(currLower + "-" + (num - 1));
                } else {
                    missingRanges.add(String.valueOf(currLower));
                }
            }
            currLower = num + 1;
        }

        if (currLower <= upper) {
            if (upper - currLower > 0) {
                missingRanges.add(currLower + "-" + upper);
            } else {
                missingRanges.add(String.valueOf(currLower));
            }
        }

        return missingRanges;
    }
}