Summary Ranges

Problem

Given a sorted integer array without duplicates, return the summary of its ranges.
For example, given [0,1,2,4,5,7] return ["0->2", "4->5", "7"].

Solution

public class Solution {
    public List<String> summaryRanges(int[] nums) {
        if (nums == null || nums.length == 0) return new ArrayList<>();
        List<String> res = new ArrayList<>();
        int start = nums[0], end = nums[0];
        for (int i = 1; i < nums.length; i++) {
            if (nums[i] - nums[i - 1] == 1) end = nums[i];
            else {
                res.add(start == end ? start + "" : start + "->" + end);
                start = end = nums[i];
            }
        }
        res.add(start == end ? start + "" : start + "->" + end); //Do not forget the last range! 
        return res;
    }
}

Analysis

The idea of this solution is similar to other Array Range problem, using start and end
We init those two vars both with nums[0], then we loop through the given nums
If we find the contiguous range, we just update the end
Otherwise, we add the current range and set both start and end to current number
At the end, we add the last range cause we don't have a chance to compare them hence we didn't add them inside the loop