#include "meetings.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
using namespace std;
using vi = vector<int>;
#define sz(x) int(x.size())
const int mx = 2'000;
int N;
set<int> edge[mx];
void cut(int u, int v)
{
edge[u].erase(v);
edge[v].erase(u);
}
void join(int u, int v)
{
edge[u].insert(v);
edge[v].insert(u);
}
vi subtree;
vi depth;
int goodct;
void dfs(int u, int p, vi& good)
{
goodct++;
for(int v : edge[u])
{
if(v == p) continue;
if(!good[v]) continue;
depth[v] = depth[u] + 1;
dfs(v, u, good);
subtree[u] += subtree[v];
}
}
vi childlist;
vi added(mx, 0);
void computelist(int u, int p, vi& newgood, vi& oldgood)
{
newgood[u] = 1;
for(int v : edge[u])
{
if(v == p) continue;
if(!oldgood[v]) continue;
computelist(v, u, newgood, oldgood);
}
}
void Locate(vi good, int X)
{
// cerr << "Locate " << X << " ";
// for(int f = 0; f < N; f++) cerr << good[f] << ' ';
// cerr << "\n";
subtree = vi(N, 1);
depth = vi(N, 1);
int rt = 0;
while(!good[rt]) rt++;
goodct = 0;
dfs(rt, rt, good);
int cent = -1;
for(int i = 0; i < N; i++)
{
if(!good[i]) continue;
if(2*subtree[i] < goodct) continue;
if(cent == -1) cent = i;
else if(depth[i] > depth[cent]) cent = i;
}
childlist.clear();
for(int x : edge[cent])
if(good[x])
childlist.push_back(x);
int desc = -1;
for(int h = 0; h+1 < sz(childlist); h++)
{
int A = childlist[h], B = childlist[h+1];
int Q = Query(A, B, X);
if(Q == A)
{
desc = A;
break;
}
else if(Q == B)
{
desc = B;
break;
}
else if(Q == cent)
{
continue;
}
else if(Q == X)
{
int Q2 = Query(cent, X, A);
if(Q2 == X)
{
cut(cent, A);
join(cent, X);
join(A, X);
added[X] = 1;
return;
}
else
{
cut(cent, B);
join(cent, X);
join(B, X);
added[X] = 1;
return;
}
}
else
{
int Q2 = Query(cent, Q, A);
if(Q2 == Q)
{
cut(cent, A);
join(cent, Q);
join(Q, A);
join(Q, X);
added[Q] = added[X] = 1;
}
else
{
cut(cent, B);
join(cent, Q);
join(Q, B);
join(Q, X);
added[Q] = added[X] = 1;
}
return;
}
}
if(desc == -1)
{
if(sz(childlist) % 2 == 1)
{
int z = childlist.back();
int Q = Query(cent, z, X);
if(Q == cent)
{
join(cent, X);
added[X] = 1;
return;
}
else if(Q == z)
{
desc = z;
}
else if(Q == X)
{
cut(cent, z);
join(cent, X);
join(X, z);
added[X] = 1;
return;
}
else
{
cut(cent, z);
join(cent, Q);
join(Q, X);
join(Q, z);
added[X] = added[Q] = 1;
return;
}
}
else
{
join(cent, X);
added[X] = 1;
return;
}
}
vi goodlist(N, 0);
computelist(desc, cent, goodlist, good);
// cerr << "desc = " << desc << '\n';
Locate(goodlist, X);
}
void Solve(int N_)
{
N = N_;
edge[0].insert(1);
edge[1].insert(0);
added[0] = added[1] = 1;
for(int X = 2; X <= N-1; X++)
{
if(added[X]) continue;
// cerr << "original new\n";
Locate(added, X);
}
for(int u = 0; u < N; u++)
for(int v : edge[u])
if(u < v)
Bridge(u, v);
}
