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"].

Analyse: 

Check whether neighbouring numbers are continuous. Push a number into the array first to avoid overflow. 

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        vector<string> result;
        if(nums.empty()) return result;
        
        int n = nums.size();
        nums.push_back(nums[n - 1]);
        n++;
        for(int i = 0; i < n - 1; i++) {
            int start = nums[i];
            while(i < n - 1 && nums[i] + 1 == nums[i + 1])
                i++;
            int end = nums[i];
            
            if(start == end)
                result.push_back(to_string(start));
            else
                result.push_back(to_string(start) + "->" + to_string(end));
        }
        return result;
    }
};