跟435题一样，都是先排序。

class Solution {
public:
    
    int removeCoveredIntervals(vector<vector<int>>& intervals) {
        int size=intervals.size();
        if(size<2)  return 0;
        sort(intervals.begin(),intervals.end(),[] (const auto& u,const auto& v){
            if(u[0]==v[0])
                return u[1]>v[1];
            else
                return u[0]<v[0];
        });
        auto it=intervals.begin();
        int res=0,second=(*it)[1];
        for(++it;it!=intervals.end();++it)
        {
            if(second>=(*it)[1])
                ++res;
            else
                second=(*it)[1];
        }
        return size-res;
    }
};