Summary Ranges

 1 class Solution {
 2 public:
 3     vector<string> summaryRanges(vector<int>& nums) {
 4         vector<string> result;
 5         
 6         if(nums.empty()) return result;
 7         int left = 0, right = left + 1;
 8         while(left < nums.size()){
 9             int gap = 1;
10             while(right < nums.size() && nums[right] - nums[left] == gap){
11                 right++;
12                 gap++;
13             }
14             result.push_back(left == right - 1 ? to_string(nums[left]) : 
15                              to_string(nums[left]) + "->" + to_string(nums[right - 1]));
16             left = right;
17             right = left + 1;
18         }
19         return result;
20     }
21 };