Submission #94097

#	Time	Username	Problem	Language	Result	Execution time	Memory
94097		qkxwsm	Shymbulak (IZhO14_shymbulak)	C++14	0 / 100	54 ms	17528 KiB

shymbulak

#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 N, M;
vi edge[MAXN];
vi nodes, cyc;
bitset<MAXN> seen, inside;
pii dp[MAXN];
ll ans;
int flag = 0;

void dfs(int u, int w)
{
	flag++; if (flag >= 1000000) exit(0);
	nodes.PB(u);
	seen[u] = true;
	for (int v : edge[u])
	{
		if (v == w)
		{
			continue;
		}
		if (inside[v])
		{
			continue;
		}
		if (seen[v])
		{
			while(nodes.back() != v)
			{
				inside[nodes.back()] = true;
				cyc.PB(nodes.back());
				nodes.pop_back();
			}
			inside[v] = true;
			cyc.PB(v);
			nodes.pop_back();
			continue;
		}
		dfs(v, u);
	}
	nodes.pop_back();
}
void solve(int u, int w)
{
	dp[u] = {0, 1};
	for (int v : edge[u])
	{
		if (v == w || inside[v]) continue;
		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;
		}
	}
}

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)
	{
		int u, v;
		cin >> u >> v;
		u--; v--;
		edge[u].PB(v);
		edge[v].PB(u);
	}
	dfs(0, -1);
	for (int u : cyc)
	{
		solve(u, -1);
		// cerr << u << ' ' << dp[u].fi << ' ' << dp[u].se << endl;
	}
	int dist = 0;
	FOR(i, 0, SZ(cyc))
	{
		int u = cyc[i];
		FOR(j, i + 1, SZ(cyc))
		{
			int v = cyc[j];
			ckmax(dist, min(j - i, SZ(cyc) + i - j) + (dp[u].fi + dp[v].fi));
		}
	}
	FOR(i, 0, SZ(cyc))
	{
		int u = cyc[i];
		FOR(j, i + 1, SZ(cyc))
		{
			int v = cyc[j];
			if (min(j - i, SZ(cyc) + i - j) + (dp[u].fi + dp[v].fi) == dist)
			{
				// cerr << u << " -> " << v << endl;
				// cerr << SZ(cyc) << ' ' << (j - i) * 2 << endl;
				ans += 1ll * dp[u].se * dp[v].se;
				if ((j - i) * 2 == SZ(cyc))
				{
					ans += 1ll * dp[u].se * dp[v].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
*/

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 50