LeetCode之Summary Ranges

class Solution {public:    vector<string> summaryRanges(vector<int>& nums) {        vector<string> res;        if(nums.empty()) return res;        int first(0);        for(int i = 0; i < nums.size(); ++i){            if(i == nums.size()-1 || nums[i+1] > nums[i] + 1){//出现新的子段                string tmp_res;                tmp_res += num2string(nums[first]);                if(i > first){                   tmp_res += "->";                   tmp_res += num2string(nums[i]);                }                res.push_back(tmp_res);                first = i+1;            }        }        return res;    }        string num2string(int num){        stringstream s;        string line;        s << num;        s >> line;        return line;     }};