Submission #1102761

#	Time	Username	Problem	Language	Result	Execution time	Memory
1102761		vjudge1	Palindromes (APIO14_palindrome)	C++17	0 / 100	31 ms	64648 KiB

palindrome

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

vector<int> cnt;
struct PAM {
    // 0 -> even root, 1 -> odd root
    static constexpr int ALPHABET_SIZE = 26;
    struct Node {
        int len, fail;
        array<int, ALPHABET_SIZE> next;
        Node() : len{}, fail{}, next{} {}
    };
    vector<int> s;
    vector<Node> t;
    PAM() { init(); }
    void init() {
        t.assign(2, Node());
        s.clear(); t[1].len = -1;
        t[0].len = 0, t[0].fail = 1;
    }
    int newNode() {
        t.emplace_back();
        cnt.emplace_back();
        return t.size() - 1;
    }
    int extend(int p, int c) {
        int n = s.size();
        s.push_back(c);
        while (s[n - t[p].len - 1] != c)
            p = t[p].fail;
        if (!t[p].next[c]) {
            int r = newNode();
            t[r].len = t[p].len + 2;
            int cur = t[p].fail;
            while (s[n - t[cur].len - 1] != c)
                cur = t[cur].fail;
            t[r].fail = t[cur].next[c];
            t[p].next[c] = r;
        }
        p = t[p].next[c];
        cnt[p]++;
        return p;
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    string s;
    cin >> s;
    int n = s.length();
    vector<int> last(n + 1);
    last[0] = 1;
    PAM pam;
    for (int i = 0; i < n; i++) {
        last[i + 1] = pam.extend(last[i], s[i] - 'a');
    }

    int sz = pam.t.size();
    // vector<int> cnt(sz);

    // for (int i = 1; i <= n; i++) {
    //     cnt[last[i]]++; // 去重 = 1
    // }
    ll ans = 0;
    for (int i = sz - 1; i > 1; i--) {
        // cnt[pam.t[i].fail] += cnt[i];
        ans = max(ans, 1LL * pam.t[i].len * cnt[i]);
    }

    cout << ans << "\n";

    return 0;
}

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