228. Summary Ranges

Summary Ranges

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"].

Credits:Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

Solution

public class Solution {
       public List<String> summaryRanges(int[] nums) {
        List<String> result = new ArrayList<>();
        if (nums == null || nums.length == 0) return result;

        int start = nums[0];
        int prev = nums[0];
        for (int i = 1; i < nums.length; i++) {
            if (prev + 1 == nums[i]) {
                prev += 1;
            } else {
                if (prev == start) {
                    result.add(String.valueOf(start));
                } else {
                    result.add(start + "->" + prev);
                }

                prev = nums[i];
                start = nums[i];
            }
        }

        if (prev == start) {
            result.add(String.valueOf(start));
        } else {
            result.add(start + "->" + prev);
        }

        return result;
    }

}