Submission #637445

#	Time	Username	Problem	Language	Result	Execution time	Memory
637445		vovamr	Lampice (COCI19_lampice)	C++17	110 / 110	4750 ms	10276 KiB

lampice

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define fi first
#define se second
#define ll long long
#define ld long double
#define sz(x) ((int)(x).size())
#define all(x) 	(x).begin(), (x).end()
#define pb push_back
#define mpp make_pair
#define ve vector
using namespace std;
using namespace __gnu_pbds;
template<class T> using oset = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
const ll inf = 1e18; const int iinf = 1e9;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
template <typename T> inline bool chmin(T& a, T b) { return (a > b ? a = b, 1 : 0); }
template <typename T> inline bool chmax(T& a, T b) { return (a < b ? a = b, 1 : 0); }

constexpr int md = 1e9 + 9; constexpr int iv2 = (md + 1) / 2;
inline int add(int a, int b) { a += b; if(a>=md){a-=md;} return a; }
inline int sub(int a, int b) { a -= b; if(a<0){a+=md;} return a; }
inline int mul(int a, int b) { return (ll)a * b % md; }
inline int bp(int a, int n) { int res = 1;
	for (; n; n >>= 1, a = mul(a, a)) {
		if (n & 1) res = mul(res, a);
	} return res;
}
inline int inv(int a) { return bp(a, md - 2); }
constexpr int p = 10039;

const int N = 5e4 + 100;

int pw[N];
inline void calc() {
	pw[0] = 1;
	for (int i = 1; i < N; ++i) pw[i] = mul(pw[i - 1], p);
}

int a[N];

ve<int> gr[N];
int used[N], sz[N];
inline void dfs1(int v, int p) {
	sz[v] = 1;
	for (auto &to : gr[v]) if (to != p && !used[to]) {
		dfs1(to, v);
		sz[v] += sz[to];
	}
}
inline int centr(int v, int p, int n) {
	for (auto &to : gr[v]) if (to != p && !used[to] && sz[to] > n / 2) {
		return centr(to, v, n);
	} return v;
}

int u[N], d[N];
inline void hashes(int v, int p, int h) {
	if (v == p) u[v] = d[v] = a[v];
	for (auto &to : gr[v]) if (to != p && !used[to]) {
		u[to] = add(u[v], mul(pw[h + 1], a[to]));
		d[to] = add(a[to], mul(pw[1], d[v]));
		hashes(to, v, h + 1);
	}
}

gp_hash_table<int,int> mp;

int cur_path[N];
int S = 0;

inline bool dfs(int v, int p, const int &l) {

	cur_path[S++] = v;
	if (S == l && u[v] == d[v]) return 1;

	int x = l + 1 - S; // other length
	int id = S - x;

	if (id >= 0 && id < S && S >= x) {
		int node = cur_path[id];
		if (u[node] == d[node]) {
			int P = !id ? 0 : d[cur_path[id - 1]];
			int H = sub(d[v], mul( P, pw[x] ));
			if (mp.find(H) != mp.end()) return 1;
		}
	}

	for (auto &to : gr[v]) {
		if (to == p || used[to]) continue;
		if (dfs(to, v, l)) return 1;
	} --S; return 0;
}

inline void add(int v, int p, const int &delta) {
	if (!(mp[d[v]] += delta)) mp.erase(d[v]);
	for (auto &to : gr[v]) if (to != p && !used[to]) {
		add(to, v, delta);
	}
}

inline bool cd(int v, int p, const int &l) {
	used[v] = 1; dfs1(v, v); hashes(v, v, 0);

	mp.clear();
	for (auto &to : gr[v]) {
		if (to == p || used[to]) continue;
		add(to, v, +1);
	}

	S = 1; cur_path[0] = v;
	for (auto &to : gr[v]) {
		if (to == p || used[to]) continue;
		add(to, v, -1);
		S = 1; if (dfs(to, v, l)) return 1;
		add(to, v, +1);
	}
	for (auto &to : gr[v]) {
		if (to == p || used[to]) continue;
		int c = centr(to, v, sz[to]);
		if (cd(c, v, l)) return 1;
	}
	return 0;
}

inline void solve() { calc();

	int n;
	cin >> n;
	for (int i = 0; i < n; ++i) {
		char x;
		cin >> x;
		a[i] = x - 'a' + 1;
	}
	for (int i = 1; i < n; ++i) {
		int v, u;
		cin >> v >> u, --v, --u;
		gr[v].pb(u), gr[u].pb(v);
	}

	dfs1(0, 0);
	int C = centr(0, 0, n);

	int answer = 0;
	int l, r, m, ans;

	// even
	l = 1, r = n / 2, ans = 0;
	while (l <= r) {
		m = l + r >> 1;
		fill(used, used + n, 0);
		if (cd(C, C, 2 * m)) ans = m, l = m + 1;
		else r = m - 1;
	} chmax(answer, 2 * ans);

	// odd
	l = ans, r = (n - 1) / 2, ans = 0;
	while (l <= r) {
		m = l + r >> 1;
		fill(used, used + n, 0);
		if (cd(C, C, 2 * m + 1)) ans = m, l = m + 1;
		else r = m - 1;
	} chmax(answer, 2 * ans + 1);

	cout << answer;
}

signed main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	int q = 1; // cin >> q;
	while (q--) solve();
	cerr << fixed << setprecision(3) << "Time execution: " << (double)clock() / CLOCKS_PER_SEC << endl;
}

Compilation message (stderr)

lampice.cpp: In function 'void solve()':
lampice.cpp:153:9: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  153 |   m = l + r >> 1;
      |       ~~^~~
lampice.cpp:162:9: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  162 |   m = l + r >> 1;
      |       ~~^~~

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