[LeetCode] Summary Ranges

This problem is similar to Missing Ranges and easier than that one.

The idea is to use two pointers to find the beginning and end of a range and then push it into the result.

The code is as follows, which should be self-explanatory.

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        vector<string> ranges;
        int left, right, n = nums.size();
        for (left = 0; left < n; left = right + 1) {
            right = left;
            while (right + 1 < n && nums[right] + 1 == nums[right + 1])
                right++;
            ranges.push_back(getRanges(nums[left], nums[right]));
        }
        return ranges;
    }
private:
    string getRanges(int low, int up) {
        return (low == up) ? to_string(low) : to_string(low) + "->" + to_string(up);
    }
};