Submission #1129501

#	Time	Username	Problem	Language	Result	Execution time	Memory
1129501		Nonoze	Lampice (COCI19_lampice)	C++20	0 / 110	4658 ms	10952 KiB

lampice

/*
*	Author: Nonoze
*	Created: Tuesday 24/12/2024
*/
#include <bits/stdc++.h>
using namespace std;

#ifndef _IN_LOCAL
	#define dbg(...)
#endif

#define endl '\n'
#define endlfl '\n' << flush
#define quit(x) return (void)(cout << x << endl)

template<typename T> void read(T& x) { cin >> x;}
template<typename T1, typename T2> void read(pair<T1, T2>& p) { read(p.first), read(p.second);}
template<typename T> void read(vector<T>& v) { for (auto& x : v) read(x); }
template<typename T1, typename T2> void read(T1& x, T2& y) { read(x), read(y); }
template<typename T1, typename T2, typename T3> void read(T1& x, T2& y, T3& z) { read(x), read(y), read(z); }
template<typename T1, typename T2, typename T3, typename T4> void read(T1& x, T2& y, T3& z, T4& zz) { read(x), read(y), read(z), read(zz); }
template<typename T> void print(vector<T>& v) { for (auto& x : v) cout << x << ' '; cout << endl; }

#define sz(x) (int)(x.size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define make_unique(v) sort(all(v)), v.erase(unique(all(v)), (v).end())
#define pb push_back
#define mp(a, b) make_pair(a, b)
#define fi first
#define se second
#define cmin(a, b) a = min(a, b)
#define cmax(a, b) a = max(a, b)
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define QYES quit("YES")
#define QNO quit("NO")

#define int long long
#define double long double
const int inf = numeric_limits<int>::max() / 4;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9+7, LOG=20;



void solve();

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	int tt=1;
	// cin >> tt;
	while(tt--) solve();
	return 0;
}


int A=27, B=1e9+7;

int fastpow(int x, int y) {
	if (!y) return 1;
	int z = fastpow(x, y/2); z = z*z % MOD;
	if (y&1) z = z*x % MOD;
	return z;
}

int inv(int x) { return fastpow(x, MOD-2); }

int n, k, m, q;
vector<int> a;
vector<vector<int>> adj;

vector<int> sz, centroid, child;
map<pair<int, int>, bool> cnt;
int obj;
bool works;


void dfs(int u, int p=-1) {
	sz[u]=1;
	for (auto v: adj[u]) if (v!=p && !centroid[v]) {
		dfs(v, u);
		sz[u]+=sz[v];
	}
}

int get_centroid(int u, int p, int tot) {
	for (auto v: adj[u]) if (v!=p && !centroid[v] && sz[v]*2>tot) return get_centroid(v, u, tot);
	return u;
}


void fill(int u, int p, int d, int hashminus, int hashplus, bool filling, int cur) {
	if (d>obj*2) return;
	int hash=(hashplus-hashminus+MOD)%MOD;
	if (d<obj) hash*=fastpow(A, obj-d);
	if (filling) {
		cnt[{d, hash}]=1;
	} else if (cnt.count({obj*2-d, hash})) {
		works=1;
	}
	// cout << hash << ' ' << d << ' ' << filling << endl;
	// cout << hashminus << ' ' << hashplus << endl;
	int newcur=cur;
	if (d>=obj) newcur=child[cur];
	for (auto v: adj[u]) if (v!=p && !centroid[v]) {
		int newhashminus = (hashminus*A)%MOD;
		int newhashplus = hashplus + fastpow(A, min(obj, d))*a[v];
		if (d>=obj) {
			newhashminus=(newhashminus+a[cur])%MOD;
			newhashplus=((newhashplus-a[cur]+MOD)*inv(A))%MOD;
		}
		child[u]=v;
		fill(v, u, d+1, newhashminus, newhashplus, filling, newcur);
	}
}

void fill2(int u, int p, int d, int hashminus, int hashplus, bool filling, int cur) {
	if (d>obj*2+1) return;
	int hash=(hashplus-hashminus+MOD)%MOD;
	if (d<obj) hash*=fastpow(A, obj-d);
	if (filling) {
		cnt[{d, hash}]=1;
	} else if (cnt.count({obj*2+1-d, hash})) {
		works=1;
	}

	// cout << hashminus << ' ' << hashplus << ' ' << hash << ' ' << d << ' ' << filling << ' ' << cur+1 << endl;
	
	int newcur=cur;
	if (d>=obj) newcur=child[cur];
	for (auto v: adj[u]) if (v!=p && !centroid[v]) {
		int newhashminus = (hashminus*A)%MOD;
		int newhashplus = hashplus + fastpow(A, min(obj, d))*a[v];
		if (d>=obj) {
			if (d>obj) newhashminus=(newhashminus+a[cur])%MOD;
			// cout << newhashplus << ' ' << a[child[cur]] << ' ' << child[cur] << endl;
			newhashplus=(((newhashplus-a[child[cur]]+MOD)%MOD)*inv(A))%MOD;
		}
		child[u]=v;
		fill2(v, u, d+1, newhashminus, newhashplus, filling, newcur);
	}
}

void decompo(int u, bool pair, int p=-1) {
	dfs(u);
	int c=get_centroid(u, -1, sz[u]); centroid[c]=1;
	cnt.clear(); cnt[{1, (a[c]*fastpow(A, obj-1))%MOD}]=1;
	// cout << (a[c]*fastpow(A, obj-1))%MOD << endl;
	for (auto v: adj[c]) if (!centroid[v]) {
		if (pair) {
			child[c]=v;
			fill(v, c, 1, 0, a[v], 0, v);
			fill(v, c, 2, 0, a[c]+A*a[v], 1, c);
		} else {
			child[n]=c, child[c]=v;
			fill2(v, c, 1, 0, a[v], 0, c);
			fill2(v, c, 2, 0, (obj>1?a[c]+A*a[v]:a[v]), 1, (obj>1?n:c));
		}
		// cout << endl;
	}
	// cout << "OK " << c+1 << endl;
	for (auto v: adj[c]) if (!centroid[v]) decompo(v, pair, c);
}


void solve() {
	read(n);
	a.clear(), a.resize(n); for (auto& u: a) {
		char x; cin >> x;
		u=x-'a'+1;
	}
	adj.clear(), adj.resize(n), child.clear(), child.resize(n+1);
	int l=2, r=n/2, ans=1;
	for (int i=1; i<n; i++) {
		int u, v; read(u, v); u--, v--;
		adj[u].pb(v), adj[v].pb(u);
		if (a[u]==a[v]) ans=2;
	}

	while (l<=r) {
		int mid=(l+r)/2;
		works=0, obj=mid, sz.clear(), sz.resize(n), centroid.clear(), centroid.resize(n);
		decompo(0, 1);
		if (works) ans=mid*2, l=mid+1;
		else r=mid-1;
	}
	
	l=1, r=(n-(1-n%2))/2;
	while (l<=r) {
		int mid=(l+r)/2;
		works=0, obj=mid, sz.clear(), sz.resize(n), centroid.clear(), centroid.resize(n);
		decompo(0, 0);
		if (works) cmax(ans, mid*2+1), l=mid+1;
		else r=mid-1;
	}


	cout << ans << endl;
}

• Subtask 1: 0 / 17
• Subtask 2: 0 / 25
• Subtask 3: 0 / 31
• Subtask 4: 0 / 37