163. Missing Ranges

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LeetCode

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Problem

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"]

Code

class Solution {
    public List<String> findMissingRanges(int[] nums, int lower, int upper) {
        List<String> res = new ArrayList<>();
        long alower = (long)lower;
        long aupper = (long)upper;

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

                alower = (long)num + 1;
            }
        }

        if(alower == aupper){
            res.add(String.valueOf(alower));
        } else if (alower < aupper){
            res.add(alower + "->" + aupper);
        }

        return res;
    }
}