#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define INF 0x3f3f3f3f
#define MOD 1000000007
#define N 500005
int dep[N], par[N];
bool bl[N];
vector<int> adj[N];
int dfs1(int v, int p){
par[v] = p;
dep[v] = dep[p] + 1;
int res = v;
for(int& x : adj[v]){
if(p == x) continue;
int w = dfs1(x, v);
if(dep[w] > dep[res])
res = w;
}
return res;
}
ll ans = 0, cnt = 1;
int d[N];
int dia;
bool ok[N];
pair<int, int> dfs3(int v, int p){
d[v] = d[p] + 1;
pair<int, int> res = {d[v], 1};
if(p != 0){
for(int& x : adj[v]){
if(x == p) continue;
pair<int, int> tmp = dfs3(x, v);
if(res.ff < tmp.ff){
res = tmp;
} else if(res.ff == tmp.ff){
res.ss += tmp.ss;
}
}
return res;
}
int t = 0;
ll cntr = 0, s = 0;
for(int& x : adj[v]){
pair<int, int> tmp = dfs3(x, v);
if(tmp.ff == dia / 2) ++t;
cntr += s * tmp.ss;
s += tmp.ss;
}
if(t > 2){
ans = 1LL * dia * dia / 2;
cnt = cntr;
}
return res;
}
pair<int, int> dfs2(int v, int p){
d[v] = d[p] + 1;
pair<int, int> res = {d[v], 1};
int sum = 0;
ll cntr = 0;
pair<int, int> b1 = {0, 0};
for(auto& x : adj[v]){
if(x == p || bl[x]) continue;
pair<int, int> tmp = dfs2(x, v);
if(tmp.ff > res.ff){
res = tmp;
} else if(tmp.ff == res.ff){
res.ss += tmp.ss;
}
if(tmp.ff + b1.ff > sum){
cntr = 1LL * tmp.ss * b1.ss;
sum = tmp.ff + b1.ff;
if(tmp.ff > b1.ff){
b1 = tmp;
} else if(tmp.ff == b1.ff){
b1.ss += tmp.ss;
}
} else if(tmp.ff + b1.ff == sum){
cntr += 1LL * tmp.ss * b1.ss;
if(tmp.ff == b1.ff){
b1.ss += tmp.ss;
}
}
}
if(ok[v] && sum != res.ff){
sum -= 2 * d[v];
ll a2 = 1LL * sum * max(dia - dep[v], dep[v]);
if(ans < a2){
ans = a2;
cnt = cntr;
} else if(ans == a2)
cnt += cntr;
}
return res;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin>>n;
dep[0] = -1;
for(int i = 1; i < n; ++i){
int v, u;
cin>>v>>u;
adj[v].push_back(u);
adj[u].push_back(v);
}
int v1 = dfs1(1, 0);
int v2 = dfs1(v1, 0);
d[0] = -1;
dia = dep[v2];
if(dia % 2 == 0){
int w = dia / 2;
int v = v2;
while(w--)
v = par[v];
dfs3(v, 0);
if(ans){
cout<<ans<<' '<<cnt<<'\n';
}
}
int qv = par[v2];
while(qv != v1){
ok[qv] = 1;
qv = par[qv];
}
if(dia % 2 == 0){
int w = dia / 2 - 1;
int u = v2;
while(w--)
u = par[u];
int u2 = par[u];
int u3 = par[u2];
bl[u3] = 1;
dfs2(u2, 0);
bl[u3] = 0;
bl[u] = 1;
dfs2(u2, 0);
bl[u] = 0;
} else {
int w = dia / 2;
int u = v2;
while(w--)
u = par[u];
int u2 = par[u];
bl[u2] = 1;
dfs2(u, 0);
bl[u2] = 0;
bl[u] = 1;
dfs2(u2, 0);
bl[u] = 0;
}
cout<<ans<<' '<<cnt;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
12 ms |
12028 KB |
Output is correct |
| 2 |
Incorrect |
13 ms |
12152 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
12 ms |
12028 KB |
Output is correct |
| 2 |
Incorrect |
13 ms |
12152 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
12 ms |
12028 KB |
Output is correct |
| 2 |
Incorrect |
13 ms |
12152 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
