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"].

 1 class Solution {
 2 public:
 3     vector<string> summaryRanges(vector<int>& nums) {
 4         vector<string> res;
 5         if (nums.empty()) {
 6             return res;
 7         }
 8         int begin = 0, end = 1;
 9         while (begin < nums.size()) {
10             if ((end < nums.size() && nums[end] != nums[end - 1] + 1) || end == nums.size()) {
11                 string range;
12                 if (end - begin == 1) {
13                     range = to_string(nums[begin]);
14                 } else {
15                     range = to_string(nums[begin]) + "->" + to_string(nums[end - 1]);
16                 }
17                 res.push_back(range);
18                 begin = end;
19             }
20             end++;
21         }
22        
23         
24         return res;
25     }
26 };