Submission #306124

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Source Code Expand

#include <bits/stdc++.h>
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(),(x).rend()
#define sz(x) ((int)(x).size())
#define REP(i,b,n) for(int i=(int)(b);i<(int)(n);++i)
#define rep(i,n) REP(i,0,n)
#define repsz(i,v) rep(i,sz(v))
#define eb emplace_back
#define mt make_tuple
#define aur auto&
#define bit(n) (1LL<<(n))
using namespace std;
typedef long long ll;
//#define int long long
static const int INF = 1<<25;
static const double EPS = 1e-5;
template<class T>bool chmin(T&a,const T&b){if(a<=b)return false;a=b;return true;}
template<class T>bool chmax(T&a,const T&b){if(a>=b)return false;a=b;return true;}

inline ll h(const ll &a, const ll &b){
    return a * 432083 + b * 93029031;
}
inline ll h(const pair<ll, ll> &a){ return h(a.first, a.second); }

bool solve(){
    int n; cin >> n;
    unordered_map<ll, int> in;
    vector<pair<ll, ll>> inv;
    rep(i, n){
        ll x, y; cin >> x >> y;
        in[h(x*2, y*2)] = i+1;
        inv.emplace_back(x*2, y*2);
    }
    rep(i, n){
        rep(j, i){
            ll x = (inv[i].first + inv[j].first) / 2;
            ll y = (inv[i].second + inv[j].second) / 2;
            ll a = inv[i].first - x;
            ll b = inv[i].second - y;
            vector<int> res;
            res.emplace_back(in[h(x+a, y+b)]);
            res.emplace_back(in[h(x-b, y+a)]);
            res.emplace_back(in[h(x-a, y-b)]);
            res.emplace_back(in[h(x+b, y-a)]);
            sort(all(res));
            res.erase(unique(all(res)), res.end());
            if(res.size() < 4) continue;
            if(res[0] == 0) continue;
            cout << 4 << endl;
            rep(i, 4) cout << res[i] << endl;
            return true;
        }
    }
    cout << 0 << endl;
    return true;
}
signed main(){
    //cin.tie(0);
    //ios_base::sync_with_stdio(0);
    cout.setf(ios::fixed); cout.precision(10);
    solve();
    return 0;
}
// vim:set foldmethod=marker commentstring=//%s:

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