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[100];
        left=0;
        right=0;
        vector<string> res;
        if(n<1)
          return res;
        for(i=0;i<n;i++)
        {
            if(i==0)
            {
                left=nums[i];
                right=left;
            }
            else if(right+1==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;
    }
};