56. Merge Intervals

class Solution {
public:
    vector<vector<int>> merge(vector<vector<int>>& intervals)
    {
        vector<vector<int>> res;

        sort(intervals.begin(), intervals.end());

        res.push_back(intervals[0]);

        if (intervals.size() == 1) return res;

        for(int i = 1; i < intervals.size(); i++)
        {

            if (intervals[i][0] <= res.back()[1])
            {
                res.back()[1] = max(res.back()[1], intervals[i][1]);
            }
            else
            {
                res.push_back(intervals[i]);
            }
        }
        return res;
    }
};

• T: $O(N \cdot N)$
• S: $O(N)$