結果

問題 No.765 ukuku 2
ユーザー りあん
提出日時 2018-12-13 00:46:51
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 1,009 ms / 3,000 ms
コード長 4,101 bytes
コンパイル時間 2,273 ms
コンパイル使用メモリ 206,960 KB
最終ジャッジ日時 2025-01-06 19:00:41
ジャッジサーバーID
（参考情報） 		judge1 / judge1
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ファイルパターン 結果
sample AC * 2
other AC * 48
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

#include<bits/stdc++.h>
using namespace std;
const int M = 1000000007;
class suffix_array {
    // compare (rank[i], rank[i + k]) and (rank[j], rank[j + k])
    static bool compare_sa(int n, const vector<int>& rank, int i, int j, int k) {
        if (rank[i] != rank[j]) return rank[i] < rank[j];
        int ri = i + k <= n ? rank[i + k] : -1;
        int rj = j + k <= n ? rank[j + k] : -1;
        return ri < rj;
    }
public:
    static vector<int> construct_sa(const string& s) {
        int n = s.length();
        vector<int> sa(n + 1), rank(n + 1);
        for (int i = 0; i <= n; ++i) {
            sa[i] = i;
            rank[i] = i < n ? s[i] : -1;
        }
        for (int k = 1; k <= n; k <<= 1) {
            sort(sa.begin(), sa.end(), [&n, &k, &rank](const int& a, const int& b){ return compare_sa(n, rank, a, b, k); });
            vector<int> tmp(n + 1);
            for (int i = 1; i <= n; ++i)
                tmp[sa[i]] = tmp[sa[i - 1]] + compare_sa(n, rank, sa[i - 1], sa[i], k);
            for (int i = 0; i <= n; ++i)
                rank[i] = tmp[i];
        }
        return sa;
    }
    static vector<int> construct_lcp(const string& s, const vector<int>& sa) {
        int n = s.length();
        vector<int> rank(n + 1), lcp(n + 1);
        for (int i = 0; i <= n; ++i) rank[sa[i]] = i;
        int h = 0;
        for (int i = 0; i < n; ++i) {
            if (h > 0) --h;
            for (int j = sa[rank[i] - 1]; j + h < n && i + h < n; ++h)
                if (s[j + h] != s[i + h]) break;
            lcp[rank[i] - 1] = h;
        }
        return lcp;
    }
};
class segtree {
private:
    int n, s, t;
    vector<int> tr;
    const int ex = M;
    int q(int k, int l, int r) {
        return r <= s || t <= l ? ex : s <= l && r <= t ? tr[k]
                : min(q(k << 1 | 1, l, (l + r) >> 1), q((k + 1) << 1, (l + r) >> 1, r));
    }
public:
    segtree(int m) {
        n = 1;
        while (n < m) n <<= 1;
        tr = vector<int>((n << 1) - 1, ex);
    }
    void update(int j, const int& x) {
        int i = j + n - 1;
        tr[i] = x;
        while (i > 0) { i = (i - 1) >> 1; tr[i] = min(tr[i << 1 | 1], tr[(i + 1) << 1]); }
    }
    // [s, t)
    int run(int _s, int _t) { s = _s; t = _t; return q(0, 0, n); }
};
int main() {
    string s;
    cin >> s;
    int n = s.length();
    int m = n * 2 + 1;
    string rev = s;
    reverse(rev.begin(), rev.end());
    string ss = s + "#" + rev;
    vector<int> sa = suffix_array::construct_sa(ss);
    vector<int> lcp = suffix_array::construct_lcp(ss, sa);
    vector<int> rank(m + 1);
    segtree sg(m + 1);
    for (int i = 0; i <= m; ++i) {
        sg.update(i, lcp[i]);
        // cout << lcp[i] << "\n";
        rank[sa[i]] = i;
    }
    int ans = 1;
    for (int i = 1; i < n; ++i) {
        {
            int ri = i, li = m - i;
            int len = sg.run(min(rank[ri], rank[li]), max(rank[ri], rank[li]));
            ri += len;
            li += len;
            ans = max(ans, len * 2 - 2);
            if (ri <= n && li + 1 <= m) {
                int len1 = sg.run(min(rank[ri], rank[li + 1]), max(rank[ri], rank[li + 1]));
                ans = max(ans, len * 2 + len1 * 2);
            }
            if (ri + 1 <= n && li <= m) {
                int len1 = sg.run(min(rank[ri + 1], rank[li]), max(rank[ri + 1], rank[li]));
                ans = max(ans, len * 2 + len1 * 2);
            }
        }
        {
            int ri = i, li = m - i + 1;
            int len = sg.run(min(rank[ri], rank[li]), max(rank[ri], rank[li]));
            ri += len;
            li += len;
            ans = max(ans, len * 2);
            if (ri <= n && li + 1 <= m) {
                int len1 = sg.run(min(rank[ri], rank[li + 1]), max(rank[ri], rank[li + 1]));
                ans = max(ans, len * 2 + len1 * 2 + 1);
            }
            if (ri + 1 <= n && li <= m) {
                int len1 = sg.run(min(rank[ri + 1], rank[li]), max(rank[ri + 1], rank[li]));
                ans = max(ans, len * 2 + len1 * 2 + 1);
            }
        }
    }
    cout << ans << "\n";
    return 0;
}
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