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) {
        
        vector<string> res;
        if(!nums.size()) return res;
        
        int i,j,left,right;
        string str;
        for(i=0;i<nums.size();i++)
        {
            left=right=nums[i];
            for(j=i+1;j<nums.size();j++)
            {
                if(nums[j]==right+1) 
                {
                    right=nums[j];
                }else
                {
                    i=j-1;break;
                }
            }
            
            if(left==right)
            {
                str=num2str(left);
            }else
            {
                str=num2str(left)+"->"+num2str(right);
            }
            res.push_back(str);
            
            if(j==nums.size()) break;
        }
        
        return res;
    }
    
    string num2str(int num)
    {
        stringstream str;
        str<<num;
        return str.str();
    }
};

//智商硬伤，一定要把语句写在break前面啊，经常忘记，怪不得死活不accept