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         int n=nums.size();
 5         int i;
 6         int left,right;
 7         char str[100];
 8         left=0;
 9         right=0;
10         vector<string> res;
11         if(n<1)
12           return res;
13         for(i=0;i<n;i++)
14         {
15             if(i==0)
16             {
17                 left=nums[i];
18                 right=left;
19             }
20             else if(right+1==nums[i])
21             {
22                 right++;
23             }
24             else
25             {
26                 if(left!=right)
27                 {
28                 sprintf(str,"%d->%d",left,right);
29                 string tmp(str);
30                 res.push_back(tmp);
31                 }
32                 else
33                 {
34                     sprintf(str,"%d",left);
35                     string tmp(str);
36                     res.push_back(tmp);
37                 }
38                 left=nums[i];
39                 right=left;
40                 
41             }
42         }
43          if(left!=right)
44                 {
45                 sprintf(str,"%d->%d",left,right);
46                 string tmp(str);
47                 res.push_back(tmp);
48                 }
49                 else
50                 {
51                     sprintf(str,"%d",left);
52                     string tmp(str);
53                     res.push_back(tmp);
54                 }
55         return res;
56     }
57 };