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"].

 class Solution {
 public:
     vector<string> summaryRanges(vector<int>& nums) {
         int n=nums.size();
         int i;
         int left,right;
         char str[];
         left=;
         right=;
         vector<string> res;
         if(n<)
           return res;
         for(i=;i<n;i++)
         {
             if(i==)
             {
                 left=nums[i];
                 right=left;
             }
             else if(right+==nums[i])
             {
                 right++;
             }
             else
             {
                 if(left!=right)
                 {
                 sprintf(str,"%d->%d",left,right);
                 string tmp(str);
                 res.push_back(tmp);
                 }
                 else
                 {
                     sprintf(str,"%d",left);
                     string tmp(str);
                     res.push_back(tmp);
                 }
                 left=nums[i];
                 right=left;
 
             }
         }
          if(left!=right)
                 {
                 sprintf(str,"%d->%d",left,right);
                 string tmp(str);
                 res.push_back(tmp);
                 }
                 else
                 {
                     sprintf(str,"%d",left);
                     string tmp(str);
                     res.push_back(tmp);
                 }
         return res;
     }
 };