제출 #162348

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
162348		amoo_safar	Palindromes (APIO14_palindrome)	C++14	47 / 100	1070 ms	66760 KiB

palindrome

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>

#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " : " << x << '\n'
#define int ll

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef string str;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef pair<pll, pll> node;
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;

const ll Mod = 1000000009LL;
const int Maxn = 3e5 + 10;
const int Maxk = 60;
const ll Inf = 2242545357980376863LL;
const ll Log = 20;
const ll Base = 998244353;

int Rank[Log][Maxn], n;
int idx[Maxn];
ll ph[Maxn], phr[Maxn], pw[Maxn];
pii a[Maxn];
str s;

ll get(int l, int r){
	return (ph[r] - (ph[l]*pw[r - l] % Mod) + Mod) % Mod;
}
ll get_rev(int l, int r){
	return (phr[l] - (phr[r]*pw[r - l] % Mod) + Mod) % Mod;
}

int pal_range(int l, int r){
	int L = 0, R = min(n - r, l) + 1, mid;
	
	//int res = 0;
	//for(int i = 0; i < R - 1; i ++) if(s[l - 1 - i] != s[r + i]) return i;
	//return R - 1;
	
	while(L + 1 < R){
		mid = (L + R) >> 1;
		if(get(l - mid, l) == get_rev(r, r + mid)) L = mid;
		else R = mid;
	}
	return L;
}

int pal[Maxn];


int eq_range(int l1, int l2){
	int L = 0, R = min(n - l1, n - l2) + 1, mid;
	//for(int i = 0; i + 1 < R; i++) if(s[i + l1] != s[i + l2]) return i;
	//return R - 1;
	while(L + 1 < R){
		mid = (L + R) >> 1;
		if(get(l1, l1 + mid) == get(l2, l2 + mid)) L = mid;
		else R = mid;
	}
	return L;
}
int eq[Maxn];

int f[Maxn], f2[Maxn];

vector<int> V;
stack<int> sta;

ll solve(){
	while(!sta.empty()) sta.pop();
	ll N = V.size();
	//cerr << "N : " << N << '\n';
	sta.push(0);
	for(int i = 1; i < N-1; i++){
		//cerr << i << " " << V[i] << '\n';
		while(V[sta.top()] > V[i]) sta.pop();
		f[i] = sta.top();
		sta.push(i);
	}
	//cerr << "S" << '\n';
	while(!sta.empty()) sta.pop();
	sta.push(N-1);
	for(int i = N-2; i > 0; i--){
		while(V[sta.top()] >= V[i]) sta.pop();
		f2[i] = sta.top();
		sta.push(i);
	}
	ll res = 0;
	
	for(int i = 1; i < N - 1; i++)
		res = max(res, 1LL * (f2[i] - f[i]) * V[i]);
	return res;
}

int32_t main(){
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	pw[0] = 1;
	for(int i = 1; i < Maxn; i++) pw[i] = (pw[i - 1] * Base) % Mod;
	
	cin >> s;
	n = s.size();
	
	ph[0] = 0;
	for(int i = 1; i <= n; i++) ph[i] = (ph[i - 1] * Base + s[i - 1]) % Mod;
	phr[n] = 0;
	for(int i = n - 1; i >= 0; i--) phr[i] = (phr[i + 1] * Base + s[i]) % Mod;
	//cerr << get(0, 2) << " " << get(n-2, n) << '\n';
	
	for(int i = 0; i < n; i++) Rank[0][i] = s[i];
	int st;
	for(int l = 1; l < Log; l++){
		st = (1 << (l - 1));
		for(int i = 0; i < n; i++){
			a[i].F = Rank[l - 1][i];
			a[i].S = (i + st < n ? Rank[l - 1][i + st] : -1); 
		}
		sort(a, a + n);
		for(int i = 0; i < n; i++)
			Rank[l][i] = lower_bound(a, a + n, pii(Rank[l - 1][i], (i + st < n ? Rank[l - 1][i + st] : -1) )) - a;
	}
	for(int i = 0; i < n; i++) idx[Rank[Log - 1][i]] = i;
	//cerr << '\n';
	//for(int i = 0; i < n; i++) cerr << s.substr(idx[i], n) << '\n';
	
	for(int i = 0; i < n - 1; i++) eq[i] = eq_range(idx[i], idx[i + 1]);
	//for(int i = 0; i < n - 1; i++) cerr << eq[i] << ' ';
	//cerr << '\n';
	
	
	ll ans = 0;
	
	for(int i = 0; i < n; i++) pal[i] = pal_range(i + 1, i);
	//for(int i = 0; i < n; i++) cerr << pal[i] << ' ';
	//cerr << '\n';
	
	for(int x = 1; x <= n; x++){
		ll cnt = (pal[idx[0]] >= x);
		ans = max(ans, cnt * (x + x - 1));
		for(int i = 1; i < n; i++){
			if(eq[i - 1] < x) cnt = 0;
			cnt += (pal[idx[i]] >= x);
			//cerr << cnt << '\n';
			ans = max(ans, cnt * (x + x - 1));
		}
	}
	/*
	V.pb(-2);
	for(int i = 0; i < n - 1; i++) V.pb( 2 * min(eq[i], min(pal[idx[i]], pal[idx[i + 1]])) - 1 );
	V.pb(-2);
	//for(auto x : V) cerr << x << ' '; cerr << '\n';
	ans = max(ans, 2LL * (*max_element(pal, pal + n)) - 1);
	
	ans = max(ans, solve());
	*/
	
	for(int i = 0; i < n; i++) pal[i] = pal_range(i, i);
	//for(int i = 0; i < n; i++) cerr << pal[i] << ' ';
	//cerr << '\n';
	/*
	V.clear();
	V.pb(-2);
	for(int i = 0; i < n - 1; i++) V.pb( 2 * min(eq[i], min(pal[idx[i]], pal[idx[i + 1]])) );
	V.pb(-2);
	//for(auto x : V) cerr << x << ' '; cerr << '\n';
	ans = max(ans, 2LL * (*max_element(pal, pal + n)));
	
	ans = max(ans, solve());
	*/
	
	for(int x = 1; x <= n; x++){
		ll cnt = (pal[idx[0]] >= x);
		ans = max(ans, cnt * (x + x - 1));
		for(int i = 1; i < n; i++){
			if(eq[i - 1] < x) cnt = 0;
			cnt += (pal[idx[i]] >= x);
			ans = max(ans, cnt * (x + x));
		}
	}
	
	cout << ans;
	return 0;
}

/*
abacaba

*/

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27