Submission #1084657

#	Time	Username	Problem	Language	Result	Execution time	Memory
1084657		anhthi	Lampice (COCI19_lampice)	C++14	110 / 110	3557 ms	11168 KiB

lampice

#include <bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define ll long long
#define mp(x, y) make_pair(x, y)
#define sz(v) ((int) (v).size())
#define all(v) (v).begin(), (v).end()
#define MASK(i) (1LL << (i))
#define BIT(x, y) (((x) >> (y)) & 1)
#define pb push_back
#define max_rng *max_element
#define min_rng *min_element
#define rep(i, n) for(int i = 1, _n = (n); i <= _n; ++i)
#define forn(i, a, b) for(int i = (a), _b = (b); i <= _b; ++i)
#define ford(i, a, b) for(int i = (a), _b = (b); i >= _b; --i)

template <class X, class Y>
    inline bool maximize(X &x, Y y) {
        return (x < y ? x = y, true : false);
    }

template <class X, class Y>
    inline bool minimize(X &x, Y y) {
        return (x > y ? x = y, true : false);
    }

template <class X>
    inline void compress(vector<X> &a) {
        sort(all(a));
        a.resize(unique(all(a)) - a.begin());
    }

int ctz(ll x) { return __builtin_ctzll(x); }
int lg(ll x) { return 63 - __builtin_clzll(x); }
int popcount(ll x) { return __builtin_popcount(x); }

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;

mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand(ll l, ll r) {
    return l + abs((ll) rng()) % (r - l + 1);
}

const ll oo = (ll) 1e17;
const int inf = (ll) 2e9 + 7, mod = (ll) 1e9 + 7;

const int mxn = 5e4 + 10, mxm = 3e6;
const int LG = 18, BASE = 311;

int n;
char a[mxn + 5];
vector<int> g[mxn + 5];

int pw[mxn + 5];

namespace CTDL {

    bool del[mxn + 5];
    int childs[mxn + 5];

    int getChilds(int u, int p) {
        childs[u] = 1;
        for (int v : g[u]) if (v != p && !del[v])
            childs[u] += getChilds(v, u);
        return childs[u];
    }
    int getCen(int u, int p, int sz) {
        for (int v : g[u]) if (v != p && !del[v]) {
            if (2 * childs[v] > sz) return getCen(v, u, sz);
        }
        return u;
    }
    int k;
    bool ans;
    int par[mxn + 5];
    int f[mxn + 5], h[mxn + 5];

    void prepare(int u, int p, int d = 1) {
        if (ans) return;
        if (d == k) {
            if (f[u] == h[u]) ans = true;
            return;
        }
        for (int v : g[u]) if (v != p && !del[v]) {
            par[v] = u;
            f[v] = (1LL * f[u] * BASE + a[v] - 'a' + 1) % mod;
            h[v] = (1LL * (a[v] - 'a' + 1) * pw[d] + h[u]) % mod;
            prepare(v, u, d + 1);
        }
        return;
    }

    gp_hash_table <int, bool> mark;

    int node[mxn + 5];
    void dfs(int u, int p, bool upd, int d = 2) {
        if (ans) return;
        if (d >= k) return;

        node[d] = u;
        if (upd) {
            int rem = k - d;
            if (d > rem) {
                int v = node[d - rem];
                if (f[v] == h[v])
                    ans = ans || mark[(f[u] - 1LL * f[par[v]] * pw[rem+1] + 1LL * mod * mod) % mod];
            }
        }
        else mark[f[u]] = true;

        for (int v : g[u]) if (v != p && !del[v])
            dfs(v, u, upd, d + 1);

        return;
    }

    void calc(int rt) {

        par[rt] = 0; node[1] = rt;

        f[rt] = h[rt] = a[rt] - 'a' + 1;
        prepare(rt, 0);

        if (ans) return;

        rep(i, 2) {
            mark.clear();
            for (int v : g[rt]) if (!del[v]) {
                dfs(v, rt, true);
                if (!ans)
                    dfs(v, rt, false);
                else return;
            }
            reverse(all(g[rt]));
        }

        return;
    }
    void solve(int u) {
        int sz = getChilds(u, 0);
        int cen = getCen(u, 0, sz);

        calc(cen);
        if (ans) return;

        del[cen] = true;
        for (int v : g[cen]) if (!del[v])
            solve(v);

        return;
    }

    bool ok(int _k) {

        k = _k;
        ans = false;
        memset(del, 0, (n + 5) * sizeof (bool));

        solve(1);

        return ans;
    }

}

int main(void) {

    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    cin >> n;
    rep(i, n) cin >> a[i];
    rep(i, n - 1) {
        int u, v;
        cin >> u >> v;
        g[u].pb(v); g[v].pb(u);
    }

    pw[0] = 1;
    rep(i, n) pw[i] = 1LL * pw[i-1] * BASE % mod;

    int ans = 1;
    for (int l = 1, r = n / 2; l <= r; ) {
        int m = (l + r) >> 1;
        if (CTDL::ok(2 * m)) {
            maximize(ans, 2 * m); l = m + 1;
        }
        else r = m - 1;
    }
    for (int l = 1, r = n / 2; l <= r; ) {
        int m = (l + r) >> 1;
        if (CTDL::ok(2 * m + 1)) {
            maximize(ans, 2 * m + 1); l = m + 1;
        }
        else r = m - 1;
    }

    cout << ans;

    return 0;
}

• Subtask 1: 17 / 17
• Subtask 2: 25 / 25
• Subtask 3: 31 / 31
• Subtask 4: 37 / 37