Missing Ranges

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

For example, given [0, 1, 3, 50, 75], lower = 0 and upper = 99, return ["2", "4->49", "51->74", "76->99"].

Solution

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

        List<String> result = new ArrayList<>();

              if (nums.length == 0) {
            String temp = toRange(lower, upper + 1);
            result.add(temp);
            return result;
        }
        if (lower < nums[0]) {
            String temp = toRange(lower, nums[0]);
            if (!temp.equals("")) {
                result.add(toRange(lower, nums[0]));
            }
        }



        for (int i = 1; i < nums.length; i++) {
            String temp;
            if (nums[i] <= upper) {
                temp = toRange(nums[i - 1] + 1, nums[i]);
            } else {
                temp = toRange(nums[i - 1] + 1, upper);
            }
            if (!temp.equals("")) {
                result.add(temp);
            }
        }

        if (nums[nums.length - 1] < upper) {
            String temp = toRange(nums[nums.length - 1] + 1, upper+1);
            if (!temp.equals("")) {
                result.add(temp);
            }
        }

        return result;
    }

    private String toRange(int start, int end) {
        if (end <= start) {
            return "";
        }

        if (end - start > 1) {
            return start + "->" + (end - 1);
        } else {
            return String.valueOf(start);
        }
    }

}