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Submission #887353

# Submission time Handle Problem Language Result Execution time Memory
887353 2023-12-14T09:56:41 Z serifefedartar Lampice (COCI19_lampice) C++17
110 / 110
 2288 ms 12124 KB 
#include <bits/stdc++.h>
using namespace std;
 
#define fast ios::sync_with_stdio(0);cin.tie(0);
typedef long long ll;
#define f first
#define s second
#define MOD 998244353
#define LOGN 21
#define MAXN 50005

const ll P = 31;
vector<vector<int>> graph;
string s;
ll marked[MAXN], sz[MAXN], powP[MAXN];
bool ch = false;
int get_sz(int node, int parent) {
	sz[node] = 1;
	for (auto u : graph[node]) {
		if (u == parent || marked[u])
			continue;
		sz[node] += get_sz(u, node);
	}
	return sz[node];
}

int find_centro(int node, int parent, int n) {
	for (auto u : graph[node]) {
		if (u != parent && !marked[u] && sz[u] * 2 >= n)
			return find_centro(u, node, n);
	}
	return node;
}

int ref_val;
set<ll> hashes[MAXN];
void eval(int node, int parent, ll normal_hash, ll rev_hash, ll dist) {
	if (ch || dist > ref_val)
		return ;
	normal_hash = (normal_hash * P + (s[node] - 'a' + 1)) % MOD;
	rev_hash = (rev_hash + powP[dist - 1] * (s[node] - 'a' + 1)) % MOD;
	if (rev_hash == normal_hash && dist == ref_val) {
		ch = true;
		return ;
	}
	if (ref_val == dist)
		return ;

	ll hash_req = (rev_hash * powP[ref_val - dist] - normal_hash + MOD) % MOD;
	if (hashes[ref_val - dist].count(hash_req))
		ch = true;

	for (auto u : graph[node]) {
		if (u == parent || marked[u])
			continue;
		eval(u, node, normal_hash, rev_hash, dist + 1);
	}
}

void add(int node, int parent, ll normal_hash, ll rev_hash, ll dist) {
	if (ch || dist > ref_val)
		return ;
	normal_hash = (normal_hash * P + (s[node] - 'a' + 1)) % MOD;
	rev_hash = (rev_hash + powP[dist - 1] * (s[node] - 'a' + 1)) % MOD;
	if (rev_hash == normal_hash && dist == ref_val) {
		ch = true;
		return ;
	}
	if (ref_val == dist)
		return ;

	ll hash_this = (rev_hash * powP[ref_val - dist] - normal_hash + MOD) % MOD;
	hashes[dist].insert(hash_this);

	for (auto u : graph[node]) {
		if (u == parent || marked[u])
			continue;
		add(u, node, normal_hash, rev_hash, dist + 1);
	}
}

void decompose(int node) {
	int n = get_sz(node, node);
	int centro = find_centro(node, node, n);
	marked[centro] = true;

	for (int i = 0; i <= sz[node]; i++)
		hashes[i].clear();
	for (auto u : graph[centro]) {
		if (!marked[u]) {
			eval(u, centro, s[centro] - 'a' + 1, s[centro] - 'a' + 1, 2);
			add(u, centro, 0, 0, 1);
		}
	}

	for (auto u : graph[centro]) {
		if (!marked[u])
			decompose(u);
	}
}

bool check(int mid) {
	ch = 0, ref_val = mid;
	for (int i = 0; i < MAXN; i++)
		marked[i] = false;
	decompose(1);
	return ch;
}

int main() {
	fast
	powP[0] = 1;
	for (int i = 1; i < MAXN; i++)
		powP[i] = (powP[i-1] * P) % MOD;
	int N, a, b;
	cin >> N >> s;
	s = "#" + s;

	graph = vector<vector<int>>(N+1, vector<int>());
	for (int i = 1; i < N; i++) {
		cin >> a >> b;
		graph[a].push_back(b);
		graph[b].push_back(a);
	}

	int L = 0;
	int R = (N - 1) / 2;
	int ans = -1;
	while (R >= L) {
		int mid = L + (R - L) / 2;
		if (check(2 * mid + 1)) {
			ans = 2 * mid + 1;
			L = mid + 1;
		} else
			R = mid - 1;
	}

	int ult_ans = ans;
	L = 1;
	R = N / 2;
	ans = -1;
	while (R >= L) {
		int mid = L + (R - L) / 2;
		if (check(2 * mid)) {
			ans = 2 * mid;
			L = mid + 1;
		} else
			R = mid - 1;
	}

	cout << max(1, max(ans, ult_ans)) << "\n";
}

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 3420 KB Output is correct
2 Correct 6 ms 3420 KB Output is correct
3 Correct 25 ms 3760 KB Output is correct
4 Correct 23 ms 3764 KB Output is correct
5 Correct 1 ms 3416 KB Output is correct
6 Correct 1 ms 3420 KB Output is correct
7 Correct 1 ms 3420 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 730 ms 10872 KB Output is correct
2 Correct 764 ms 11100 KB Output is correct
3 Correct 570 ms 11356 KB Output is correct
4 Correct 675 ms 11868 KB Output is correct
5 Correct 990 ms 12124 KB Output is correct
6 Correct 339 ms 10844 KB Output is correct

Subtask #3
31.0 / 31.0

# Verdict Execution time Memory Grader output
1 Correct 1635 ms 9820 KB Output is correct
2 Correct 2001 ms 9564 KB Output is correct
3 Correct 1936 ms 9700 KB Output is correct
4 Correct 1869 ms 8864 KB Output is correct
5 Correct 1692 ms 9052 KB Output is correct
6 Correct 1490 ms 8656 KB Output is correct

Subtask #4
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 3420 KB Output is correct
2 Correct 6 ms 3420 KB Output is correct
3 Correct 25 ms 3760 KB Output is correct
4 Correct 23 ms 3764 KB Output is correct
5 Correct 1 ms 3416 KB Output is correct
6 Correct 1 ms 3420 KB Output is correct
7 Correct 1 ms 3420 KB Output is correct
8 Correct 730 ms 10872 KB Output is correct
9 Correct 764 ms 11100 KB Output is correct
10 Correct 570 ms 11356 KB Output is correct
11 Correct 675 ms 11868 KB Output is correct
12 Correct 990 ms 12124 KB Output is correct
13 Correct 339 ms 10844 KB Output is correct
14 Correct 1635 ms 9820 KB Output is correct
15 Correct 2001 ms 9564 KB Output is correct
16 Correct 1936 ms 9700 KB Output is correct
17 Correct 1869 ms 8864 KB Output is correct
18 Correct 1692 ms 9052 KB Output is correct
19 Correct 1490 ms 8656 KB Output is correct
20 Correct 1328 ms 7864 KB Output is correct
21 Correct 1589 ms 8788 KB Output is correct
22 Correct 2288 ms 9052 KB Output is correct
23 Correct 509 ms 7260 KB Output is correct
24 Correct 1823 ms 8284 KB Output is correct
25 Correct 1416 ms 8024 KB Output is correct
26 Correct 1811 ms 9812 KB Output is correct
27 Correct 2009 ms 9552 KB Output is correct
28 Correct 1236 ms 7316 KB Output is correct
29 Correct 1292 ms 7388 KB Output is correct
30 Correct 1451 ms 9028 KB Output is correct
31 Correct 1323 ms 8024 KB Output is correct
32 Correct 1260 ms 9812 KB Output is correct
33 Correct 1102 ms 9296 KB Output is correct