class Solution {

public:

    vector<vector<int>> merge(vector<vector<int>>& intervals) {

        int n = intervals.size();

        vector<vector<int>> res;

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

        int j = 0;

        res.push_back(intervals[0]);

        for (int i = j + 1; i < n; i++) {

            // When the right of the current interval is bigger than the left of the

            // next interval, merge them

            if (intervals[i][0] <= res[j][1]) {

            res[j][1] = max(res[j][1], intervals[i][1]);

            } else {

            // On the contrary, add the current interval to the result

            res.push_back(intervals[i]);

            j++;

            }

        }

        return res;

    }

};