Submission #1077264

#	Time	Username	Problem	Language	Result	Execution time	Memory
1077264		Ejen	Lampice (COCI19_lampice)	C++17	110 / 110	2963 ms	10800 KiB

lampice

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

#define el "\n"
#define fu(i, a, b) for (int i = a; i <= b; ++i)
#define fd(i, a, b) for (int i = a; i >= b; --i)
#define ff first
#define ss second
#define all(v) (v).begin(), (v).end()
#define sz(v) (ll)(v).size()
#define mask(i) (1LL << (i))
#define bit(x, i) ((x) >> (i) & 1)
 
using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
 
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
 
ll Rand(ll l, ll r) {
    return uniform_int_distribution<ll>(l, r) (rng);
}
 
ll last(ll msk)     {return msk & (-msk);}
ll pop_cnt(ll msk)  {return __builtin_popcountll(msk);}
ll ctz(ll msk)      {return __builtin_ctzll(msk);}
ll lg(ll msk)       {return 63 - __builtin_clzll(msk);}
 
template<class T1, class T2> bool minimize(T1 &a, T2 b) {
    return a > b ? a = b, 1 : 0;
}
 
template<class T1, class T2> bool maximize(T1 &a, T2 b) {
    return a < b ? a = b, 1 : 0;
}
 
template<class T> void print(T a) {
    for (auto x : a) cout << x << " ";
    cout << el;
}
 
template<class T> void compress(T &a) {
    sort(all(a));
    a.resize(unique(all(a)) - a.begin());
}
 
const long long N = 5e4 + 2, mod = 1e9 + 7, inf = 2e18, bl = 320, lim = 1e6 + 27, base = 311;
 
int n, sz;
string s;
int child[N], h[N];
int hashUp[N], hashDown[N], pw[N], save[N];
bool del[N], ok[N];
basic_string<int> adj[N];
gp_hash_table <int, bool> mp;
 
void countChild(int u, int p) {
    child[u] = 1;
    // cout << u << ' '  << child[u] << el;
    for (int v : adj[u]) {
        if (v == p || del[v]) continue;
        countChild(v, u);
        child[u] += child[v];
    }
    // cout << child[u] << ' ';
}
 
int centroid(int u, int p, int root) {
    for (int v : adj[u]) {
        if (v == p || del[v] || child[v] <= child[root] / 2) continue;
        return centroid(v, u, root);
    }
    return u;
}
 
void dfs(int u, int p, int len) {
    if (h[u] > len) return;
    hashUp[u] = (1LL * s[u] * pw[h[u] - 1] + hashUp[p]) % mod;
    hashDown[u] = (1LL * hashDown[p] * base + s[u]) % mod;
    for (int v : adj[u]) {
        if (v == p || del[v]) continue;
        h[v] = h[u] + 1;
        dfs(v, u, len);
    }
}
 
void dfsUpdate(int u, int p, int len) {
    if (h[u] > len) return;
    if (2 * h[u] > len) {
        int par = 2 * h[u] - len;
        if (ok[par]) mp[(1LL * hashDown[u] - 1LL * save[par - 1] * pw[h[u] - par + 1] + mod * mod) % mod] = true;
    }
    if (h[u] > len) return;
    save[h[u]] = hashDown[u];
    if (hashDown[u] == hashUp[u]) ok[h[u]] = true;
    for (int v : adj[u]) {
        if (v == p || del[v]) continue;
        dfsUpdate(v, u, len);
    }
    ok[h[u]] = false;
}
 
bool dfsSearch(int u, int p, int len) {
    if (h[u] > len) return false;
    if (mp[hashDown[u]]) return true;
    if (h[u] == len && hashUp[u] == hashDown[u]) return true;
    for (int v : adj[u]) {
        if (v == p || del[v]) continue;
        if (dfsSearch(v, u, len)) return true;
    }
    return false;
}
 
bool check(int u, int len) {
    countChild(u, 0);
    int root = centroid(u, 0, u);
    h[root] = 1;
    dfs(root, 0, len);
    ok[1] = true;
    save[1] = hashDown[root];
    fu(turn, 0, 1) {
        mp.clear();
        for (int x : adj[root]) {
            if (del[x]) continue;
            if (dfsSearch(x, root, len)) return true;
            dfsUpdate(x, root, len);
        }
        reverse(all(adj[root]));
    }
    del[root] = true;
    for (int v : adj[root]) {
        if (del[v]) continue;
        if (check(v, len)) return true;;
    }
    return false;
}
 
signed main() {
//    freopen("bai3.inp", "r", stdin);
//    freopen("bai3.out", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> s;
    s = ' ' + s;
    sz = sz(s) - 1;
    pw[0] = 1;
    fu(i, 1, n) pw[i] = 1LL * pw[i - 1] * base % mod;
    fu(i, 2, n) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    // cout << check(1, 6);
    int res = 1;
    int l = 1, r = n / 2;
    while (l <= r) {
        int mid = (r + l) / 2;
        fu(i, 1, n) del[i] = 0;
        if (check(1, 2 * mid)) {
            res = 2 * mid;
            l = mid + 1;
        }
        else r = mid - 1;
    }
    l = 1, r = n / 2;
    while (l <= r) {
        int mid = (l + r) / 2;
        fu(i, 1, n) del[i] = 0;
        if (check(1, 2 * mid + 1)) {
            maximize(res, 2 * mid + 1);
            l = mid + 1;
        }
        else r = mid - 1;
    }

    cout << res;
    cerr << "\nTime elapsed: " << (1.0 * clock() / CLOCKS_PER_SEC) << " ms.";
}

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