#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
random_device(rd);
mt19937 rng(rd());
const long long FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
struct custom_hash
{
template<class T>
unsigned long long operator()(T v) const
{
unsigned long long x = v;
x += FIXED_RANDOM;
// x += 11400714819323198485ull;
// x = (x ^ (x >> 30)) * 13787848793156543929ull;
x = (x ^ (x >> 27)) * 10723151780598845931ull;
return x ^ (x >> 31);
}
};
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T, class U> using hash_table = gp_hash_table<T, U, custom_hash>;
template<class T>
T randomize(T mod)
{
return (uniform_int_distribution<T>(0, mod - 1))(rng);
}
template<class T>
void readi(T &x)
{
x = 0;
bool negative = false;
char c = ' ';
while (c < '-')
{
c = getchar();
}
if (c == '-')
{
negative = true;
c = getchar();
}
while (c >= '0')
{
x = x * 10 + (c - '0');
c = getchar();
}
if (negative)
{
x = -x;
}
}
template<class T>
void printi(T output)
{
if (output == 0)
{
putchar('0');
return;
}
if (output < 0)
{
putchar('-');
output = -output;
}
int buf[20], n = 0;
while(output)
{
buf[n] = ((output % 10));
output /= 10;
n++;
}
for (n--; n >= 0; n--)
{
putchar(buf[n] + '0');
}
return;
}
template<class T>
void ckmin(T &a, T b)
{
a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
a = max(a, b);
}
long long expo(long long a, long long e, long long mod)
{
return ((e == 0) ? 1 : ((expo(a * a % mod, e >> 1, mod)) * ((e & 1) ? a : 1) % mod));
}
template<class T, class U>
void nmod(T &x, U mod)
{
if (x >= mod) x -= mod;
}
template<class T>
T gcd(T a, T b)
{
return (b ? gcd(b, a % b) : a);
}
#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define DBG(x) cerr << #x << " = " << (x) << endl
#define SZ(x) ((int) ((x).size()))
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)
#define ALL(x) (x).begin(), (x).end()
const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-9;
#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 200013
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<ld> vd;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
typedef vector<pdd> vpd;
int U, V, N, M;
int dsu[MAXN];
int parent[MAXN], depth[MAXN];
vi edge[MAXN], edge1[MAXN];
vi cyc;
bitset<MAXN> inside;
pii dp[MAXN], dp1[MAXN];
int diam = 0;
ll ans;
vi nodes;
vector<pair<int, ll> > res;
int get(int u)
{
return (u == dsu[u] ? u : dsu[u] = get(dsu[u]));
}
void DFS(int u)
{
for (int v : edge[u])
{
if (v == parent[u]) continue;
if (u == U && v == V) continue;
if (u == V && v == U) continue;
parent[v] = u;
// cerr << u << " -> " << v << endl;
DFS(v);
}
}
bool merge(int u, int v)
{
u = get(u);
v = get(v);
if (u == v) return false;
dsu[u] = v;
return true;
}
void solve(int u, int w)
{
nodes.PB(u);
dp[u] = {0, 1};
for (int v : edge[u])
{
if (v == w || inside[v]) continue;
edge1[v].PB(u);
edge1[u].PB(v);
solve(v, u);
if (dp[v].fi + 1 > dp[u].fi)
{
dp[u].fi = dp[v].fi + 1;
dp[u].se = dp[v].se;
}
else if (dp[v].fi + 1 == dp[u].fi)
{
dp[u].se += dp[v].se;
}
}
}
void dfs(int u)
{
for (int v : edge1[u])
{
if (v == parent[u]) continue;
parent[v] = u;
depth[v] = depth[u] + 1;
dfs(v);
}
}
void dfs1(int u)
{
dp1[u] = {0, 1};
for (int v : edge1[u])
{
if (v == parent[u]) continue;
dfs1(v);
pii p = {dp1[v].fi + 1, dp1[v].se};
ckmax(diam, p.fi + dp1[u].fi);
if (p.fi == dp1[u].fi)
{
dp1[u].se += p.se;
}
else if (p.fi > dp1[u].fi)
{
dp1[u] = p;
}
}
}
void dfs2(int u)
{
int big = 0; ll num = 0, tot = 0;
for (int v : edge1[u])
{
if (v == parent[u]) continue;
dfs2(v);
}
for (int v : edge1[u])
{
if (v == parent[u]) continue;
ckmax(big, dp1[v].fi + 1);
}
for (int v : edge1[u])
{
if (v == parent[u]) continue;
if (dp1[v].fi + 1 == big)
{
tot += dp1[v].se;
}
}
for (int v : edge1[u])
{
if (v == parent[u]) continue;
if (dp1[v].fi + 1 + big == diam)
{
ans += dp1[v].se * (dp1[v].fi + 1 == big ? num : tot);
}
if (dp1[v].fi + 1 == big)
{
num += dp1[v].se;
}
}
if (big == diam)
{
ans += num;
}
}
int32_t main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
// cout << fixed << setprecision(10);
// cerr << fixed << setprecision(10);
// if (fopen("file.in", "r"))
// {
// freopen ("file.in", "r", stdin);
// freopen ("file.out", "w", stdout);
// }
cin >> N;
FOR(i, 0, N) dsu[i] = i;
FOR(i, 0, N)
{
int u, v;
cin >> u >> v;
u--; v--;
edge[u].PB(v);
edge[v].PB(u);
if (!merge(u, v))
{
U = u; V = v;
// DBG(U); DBG(V);
}
}
FOR(i, 0, N) parent[i] = N;
DFS(U);
while(V != N)
{
cyc.PB(V);
inside[V] = true;
V = parent[V];
}
M = SZ(cyc);
for (int u : cyc)
{
solve(u, -1);
for (int v : nodes)
{
depth[v] = 0;
parent[v] = N;
}
dfs(u);
dfs1(u);
dfs2(u);
res.PB({diam, ans});
diam = 0; ans = 0;
nodes.clear();
// cerr << u << ' ' << diam << ' ' << ans << endl;
}
FOR(i, 0, M)
{
int u = cyc[i];
FOR(j, i + 1, M)
{
int v = cyc[j];
ckmax(diam, min(j - i, M + i - j) + (dp[u].fi + dp[v].fi));
}
}
FOR(i, 0, M)
{
int u = cyc[i];
FOR(j, i + 1, M)
{
int v = cyc[j];
if (min(j - i, M + i - j) + (dp[u].fi + dp[v].fi) == diam)
{
// cerr << u << " -> " << v << endl;
// cerr << M << ' ' << (j - i) * 2 << endl;
ans += 1ll * dp[u].se * dp[v].se;
if ((j - i) * 2 == M)
{
ans += 1ll * dp[u].se * dp[v].se;
}
}
}
}
res.PB({diam, ans});
// cerr << diam << ' ' << ans << endl;
diam = 0; ans = 0;
FOR(i, 0, SZ(res))
{
ckmax(diam, res[i].fi);
}
FOR(i, 0, SZ(res))
{
if (res[i].fi == diam)
{
ans += res[i].se;
}
}
cout << ans << '\n';
// cerr << "time elapsed = " << (clock() / (CLOCKS_PER_SEC / 1000)) << " ms" << endl;
return 0;
}
/* READ READ READ
* int overflow, maxn too small, special cases (n=1?, two distinct?), cin.tie() interactive
* reread the problem, try small cases
* note down possible sources of error as you go
* do smth instead of nothing
*/
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
10 ms |
9720 KB |
Output is correct |
| 2 |
Correct |
10 ms |
9720 KB |
Output is correct |
| 3 |
Correct |
10 ms |
9720 KB |
Output is correct |
| 4 |
Correct |
10 ms |
9720 KB |
Output is correct |
| 5 |
Correct |
9 ms |
9720 KB |
Output is correct |
| 6 |
Correct |
9 ms |
9848 KB |
Output is correct |
| 7 |
Correct |
11 ms |
9720 KB |
Output is correct |
| 8 |
Correct |
10 ms |
9720 KB |
Output is correct |
| 9 |
Correct |
10 ms |
9720 KB |
Output is correct |
| 10 |
Correct |
9 ms |
9720 KB |
Output is correct |
| 11 |
Correct |
11 ms |
9720 KB |
Output is correct |
| 12 |
Correct |
10 ms |
9724 KB |
Output is correct |
| 13 |
Correct |
10 ms |
9848 KB |
Output is correct |
| 14 |
Correct |
11 ms |
9848 KB |
Output is correct |
| 15 |
Correct |
11 ms |
9848 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
11 ms |
9848 KB |
Output is correct |
| 2 |
Correct |
11 ms |
9848 KB |
Output is correct |
| 3 |
Correct |
11 ms |
9848 KB |
Output is correct |
| 4 |
Correct |
11 ms |
9848 KB |
Output is correct |
| 5 |
Correct |
13 ms |
10232 KB |
Output is correct |
| 6 |
Correct |
13 ms |
10232 KB |
Output is correct |
| 7 |
Correct |
14 ms |
10232 KB |
Output is correct |
| 8 |
Correct |
14 ms |
10236 KB |
Output is correct |
| 9 |
Correct |
12 ms |
10364 KB |
Output is correct |
| 10 |
Correct |
14 ms |
10360 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
87 ms |
18752 KB |
Output is correct |
| 2 |
Correct |
102 ms |
20820 KB |
Output is correct |
| 3 |
Execution timed out |
1550 ms |
21996 KB |
Time limit exceeded |
| 4 |
Halted |
0 ms |
0 KB |
- |
