题目

#include<bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 2e5 + 5;
int n;
struct Poi{int x, y;// Poi() = default;// Poi(int x, int y): x(x), y(y) {}Poi operator-(Poi u){// Poi res = {abs(x - u.x), abs(y - u.y)};不能直接都取绝对值// return res;return Poi{(x - u.x), (y - u.y)};}Poi operator+(Poi u){return Poi{x + u.x, y + u.y};}bool operator<(const Poi &u)const{//整段不能去掉，不然报错if(x != u.x) return x < u.x;return y < u.y;}
}point[maxn];
bool mp[maxn];
map<Poi, int> cnt;
bool check(Poi d){// for(int i = 1; i <= 2 * n; i++){// 	mp[i] = 0;// }int match = 0;int dx = d.x, dy = d.y;// for(int i = 1; i <= 2 * n; i++){// 	if(mp[i]) continue;// 	for(int j = i + 1; j <= 2 * n; j++){// 		Poi dd = point[i] - point[j];// 		if((dd.x == d.x && dd.y == dd.y)){// 			mp[i] = 1;// 			mp[j] = 1;// 			break;// 		}// 	}// 	if(!mp[i]) return 0;// }// return 1;map<Poi, int> tmp = cnt;for(int i = 1; i <= 2 * n; i++){int x = point[i].x, y = point[i].y;Poi u = {x + dx, y + dy};if(tmp[u] && tmp[point[i]]){tmp[u]--;tmp[point[i]]--;match++;}}return match == n;
}
void solve(){map<Poi, bool> vis;cnt.clear();int i, j;cin >> n;for(i = 1; i <= 2 * n; i++){cin >> point[i].x >> point[i].y;cnt[point[i]]++;}Poi d;vector<Poi> ans;for(i = 2; i <= 2 * n; i++){d = point[1] - point[i];if(d.x < 0) d.x = -d.x, d.y = -d.y;if(vis[d]) continue;vis[d] = 1;bool flag = 1;for(int j = 2; j <= 2 * n; j++){Poi u = point[j] + d;Poi v = point[j] - d;if(!cnt[u] && !cnt[v]){flag = 0;break;}}if(!flag) continue;if(check(d)){ans.push_back(d);if(!(d.x == 0 && d.y == 0)) ans.push_back({-d.x, -d.y});}}cout << ans.size() << '\n';sort(ans.begin(), ans.end());for(auto p : ans){cout << p.x << ' ' << p.y << '\n';}
}
signed main(){ios::sync_with_stdio(0);cin.tie(0);int T;cin >> T;while(T--){solve();}return 0;
}