Submission #41991

#	Time	Username	Problem	Language	Result	Execution time	Memory
41991		RockyB	Palindromes (APIO14_palindrome)	C++14	23 / 100	1070 ms	5612 KiB

palindrome

/// In The Name Of God

#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#include <bits/stdc++.h>

#define f first
#define s second

#define pb push_back
#define pp pop_back
#define mp make_pair

#define sz(x) (int)x.size()
#define sqr(x) ((x) * 1ll * (x))
#define all(x) x.begin(), x.end()

#define Kazakhstan ios_base :: sync_with_stdio(0), cin.tie(0), cout.tie(0);

#define nl '\n'
#define ioi exit(0);

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

const int N = (int)3e5 + 7;
const int inf = (int)1e9 + 7;
const int mod = (int)1e9 + 7;
const ll linf = (ll)1e18 + 7;

const int dx[] = {-1, 0, 1, 0, 1, -1, -1, 1};
const int dy[] = {0, 1, 0, -1, 1, -1, 1, -1};

using namespace std;

void add(int &x, int y) {
	x += y;
	if (x >= mod) x -= mod;
	if (x < 0) x += mod;
}
int sum(int x, int y) {
	add(x, y);
	return x;
}
int mult(int x, int y) {
	return x * 1ll * y % mod;
}


int n;
int p[N];
char s[N];

ll ans;

const int p1 = 997;
struct hsh {
	int len;
	int h[N], dg[N];
	void init(char *x) {
		len = strlen(x + 1);
		dg[0] = 1;
		dg[1] = p1;
		for (int i = 1; i <= len; i++) {
			h[i + 1] = sum(mult(h[i], p1), x[i]);
			dg[i + 1] = mult(dg[i], p1);
		}
	}
	ll get(int l, int r) {
		return sum(h[r + 1], -mult(h[l], dg[r - l + 1]));
	}
} t, t1;

bool check(int l, int r) {
	return t.get(l, r) == t1.get(n - r + 1, n - l + 1);
}
ll get(int len) {
	int mx = 0;
	unordered_map <int, int> cnt;
	for (int i = len; i <= n; i++) {
		if (!check(i - len + 1, i)) continue;
		mx = max(mx, ++cnt[t.get(i - len + 1, i)]);
	}
	return (ll)mx * len;
}

int main() {
	#ifdef IOI2018
		freopen ("in.txt", "r", stdin);
		//freopen ("slow.out", "w", stdout);
	#endif
	Kazakhstan
	cin >> (s + 1);
	n = strlen(s + 1);
	t.init(s);
	reverse(s + 1, s + 1 + n);
	t1.init(s);
	reverse(s + 1, s + 1 + n);
	for (int i = 1; i <= n; i++) {
		ans = max(ans, get(i));
	}
	cout << ans;
	ioi
}

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