제출 #734210

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
734210		SanguineChameleon	회문 (APIO14_palindrome)	C++17	100 / 100	351 ms	47760 KiB

palindrome

#include <bits/stdc++.h>
using namespace std;

void just_do_it();

int main() {
	#ifdef KAMIRULEZ
		freopen("kamirulez.inp", "r", stdin);
		freopen("kamirulez.out", "w", stdout);
	#endif
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	just_do_it();
	return 0;
}

const int maxn = 3e5 + 20;
const int maxL = 20;
int pal[maxn * 2];
int a[maxn * 2];
int eq[maxn];
pair<int, int> pair_eq[maxn];
int nxt_eq[maxn];
int pos[maxn];
int perm[maxn];
int nxt_perm[maxn];
int lcp[maxn];
vector<pair<int, int>> q_join[maxn];
vector<int> q_add[maxn];
int sz[maxn];
int depth[maxn];
int par[maxn];

int root(int u) {
	if (par[u] == -1) {
		return u;
	}
	return (par[u] = root(par[u]));
}

void update(int u, int v) {
	int ru = root(u);
	int rv = root(v);
	if (ru == rv) {
		return;
	}
	if (depth[ru] > depth[rv]) {
		swap(ru, rv);
	}
	par[ru] = rv;
	sz[rv] += sz[ru];
	if (depth[ru] == depth[rv]) {
		depth[rv]++;
	}
	return;
}

void just_do_it() {
	string s;
	cin >> s;
	int n = s.size();
	for (int i = 0; i < n * 2 + 1; i++) {
		if (i % 2 == 1) {
			a[i] = s[i / 2] - 'a';
		}
		else {
			a[i] = -1;
		}
	}
	int lt = -1;
	int rt = -1;
	for (int i = 0; i < n * 2 + 1; i++) {
		pal[i] = (i <= rt ? min(rt - i + 1, pal[lt + rt - i]) : 0);
		while (i - pal[i] >= 0 && i + pal[i] < n * 2 + 1 && a[i - pal[i]] == a[i + pal[i]]) {
			pal[i]++;
		}
		if (i + pal[i] - 1 > rt) {
			lt = i - pal[i] + 1;
			rt = i + pal[i] - 1;
		}
	}
	for (int i = 0; i < n; i++) {
		a[i] = s[i] - 'a' + 1;
	}
	a[n++] = 0;
	for (int i = 0; i < n; i++) {
		pos[a[i]]++;
	}
	int cnt = 0;
	for (int i = 0; i <= 26; i++) {
		swap(cnt, pos[i]);
		cnt += pos[i];
	}
	for (int i = 0; i < n; i++) {
		perm[pos[a[i]]++] = i;
	}
	cnt = 0;
	for (int i = 0; i < n; i++) {
		if (i > 0 && a[perm[i - 1]] != a[perm[i]]) {
			cnt++;
		}
		eq[perm[i]] = cnt;
	}
	for (int k = 0; k < maxL; k++) {
		for (int i = 0; i < n; i++) {
			pos[i] = 0;
		}
		for (int i = 0; i < n; i++) {
			pos[eq[i]]++;
		}
		cnt = 0;
		for (int i = 0; i < n; i++) {
			swap(cnt, pos[i]);
			cnt += pos[i];
		}
		for (int i = 0; i < n; i++) {
			int j = (perm[i] - (1 << k)) % n;
			if (j < 0) {
				j += n;
			}
			nxt_perm[pos[eq[j]]++] = j;
		}
		cnt = 0;
		for (int i = 0; i < n; i++) {
			pair_eq[i] = make_pair(eq[nxt_perm[i]], eq[(nxt_perm[i] + (1 << k)) % n]);
		}
		for (int i = 0; i < n; i++) {
			if (i > 0 && pair_eq[i] != pair_eq[i - 1]) {
				cnt++;
			}
			nxt_eq[nxt_perm[i]] = cnt;
		}
		swap(eq, nxt_eq);
		swap(perm, nxt_perm);
	}
	for (int i = 0; i < n; i++) {
		pos[perm[i]] = i;
	}
	int cur = 0;
	for (int i = 0; i < n; i++) {
		if (pos[i] == n - 1) {
			continue;
		}
		int j = perm[pos[i] + 1];
		while (i + cur < n && j + cur < n && a[i + cur] == a[j + cur]) {
			cur++;
		}
		lcp[pos[i]] = cur;
		if (cur > 0) {
			cur--;
		}
	}
	n--;
	long long res = 0;
	for (int k = 0; k < 2; k++) {
		for (int i = 0; i <= n; i++) {
			q_join[i].clear();
			q_add[i].clear();
		}
		for (int i = 0; i < n; i++) {
			q_add[pal[i * 2 + k] / 2].push_back(i);
		}
		for (int i = 0; i < n; i++) {
			int u = perm[i];
			int v = perm[i + 1];
			q_join[lcp[i]].emplace_back(u, v);
		}
		int max_sz = 0;
		for (int i = 0; i < n; i++) {
			par[i] = -1;
			depth[i] = 0;
			sz[i] = 0;
		}
		for (int i = n; i >= 1; i--) {
			for (auto u: q_add[i]) {
				max_sz = max(max_sz, ++sz[root(u)]);
			}
			for (auto p: q_join[i]) {
				int u = p.first;
				int v = p.second;
				update(u, v);
				max_sz = max(max_sz, sz[root(u)]);
			}
			res = max(res, 1LL * (i * 2 - k) * max_sz);
		}
	}
	cout << res;
}

// END MAIN CODE

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 26 / 26
• Subtask 5: 27 / 27