leetcode merge-intervals

#include <algorithm>
class Solution {
public:
    vector<vector<int>> merge(vector<vector<int>>& inter) {
        vector<pair<int, int>> intervals;
        for(int i = 0; i < inter.size(); i++){
            intervals.push_back({inter[i][0], inter[i][1]});
        }
        sort(intervals.begin(), intervals.end());

        vector<vector<int>> v;
        set<pair<int, int>> s;
        for(int i = 0; i < intervals.size(); i++){
            pair<int, int> t = intervals[i];
            if(s.find(t) == s.end()){
                int k = t.second, p = t.first;
                s.insert(t);
                for(int j = i+1; j < intervals.size(); j++){
                    if(k >= intervals[j].first){
                        if(s.find(intervals[j]) == s.end()){
                            s.insert(intervals[j]);
                            t = intervals[j];
                            k = max(k, t.second);
                            p = min(p, t.first);
                        }
                    }
                }
                v.push_back({p, k});
            }

        }

        return v;
    }
};