228 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"].

Solution

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