class Solution {

public:

bool isReflected(vector<pair<int, int>>& points)

{

int N=points.size();

if (N==0) return true;

unordered_map<int,set<int>>Map;

unordered_set<int>Set;

for (int i=0; i<N; i++)

{

Map[points[i].second].insert(points[i].first);

Set.insert(points[i].first);

}

float x0=0;

for (auto a:Set)

x0+=a;

x0=x0/Set.size();

for (auto a:Map)

{

vector<int>q(a.second.begin(),a.second.end());

int i=0;

int j=q.size()-1;

while (i<=j)

{

if (q[i]+q[j]!=x0*2)

return false;

i++;

j--;

}

}

return true;

}

};