Submission #640683

#	Time	Username	Problem	Language	Result	Execution time	Memory
640683		LeonaRaging	Lampice (COCI19_lampice)	C++14	110 / 110	4957 ms	15104 KiB

lampice

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

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

using namespace __gnu_pbds;
using namespace std;

#define fi first
#define se second
#define ll long long
#define pb push_back
#define db(val) "[" #val " = " << (val) << "] "

const ll mod = 1e9 + 7;
const int maxn = 1e5 + 4;
const int INF = 1e9;
const ll base = 31;
const int N = 16;

int n, len, root, used[maxn], h[maxn];
string s;
vector<int> adj[maxn], nodes;
ll Pow[maxn], up[maxn], down[maxn];
gp_hash_table<ll,int> L;
bool flag;

ll add(ll a, ll b) {
    a += b;
    return a;
}

ll del(ll a, ll b) {
    a -= b;
    return a;
}

void pre(int u, int p) {
    if (p) 
        down[u] = add(down[p], (s[u] - 'a' + 1) * Pow[h[u] - 1]);
    if (p) 
        up[u] = add(up[p] * base, s[u] - 'a' + 1);
    L[up[u]]++;
    for (int v : adj[u])
        if (v != p && !used[v]) {
            h[v] = h[u] + 1;
            pre(v, u);
        }
}

void dfs(int u, int p) {
    if (len < h[u] || flag) return;
    nodes.pb(u);
    int k = len - h[u] - 1, c = 0;
    if (int(nodes.size()) > h[u] - k && h[u] - k >= 0)
        c = nodes[h[u] - k];
    if (c && add(up[c], (s[root] - 'a' + 1) * Pow[h[c]]) == 
            add(down[c] * base, (s[root] - 'a' + 1))) {
        if (k == 0)
            return flag = true, void();
        ll val = del(up[u], up[c] * Pow[k]) ;
        if (L.find(val) != L.end()) {
            return flag = true, void();
        }
    }
    for (int v : adj[u])
        if (v != p && !used[v])
            dfs(v, u);
    nodes.pop_back();
}

void reset(int u, int p, int val) {
    L[up[u]] += val;
    if (L[up[u]] == 0)
        L.erase(up[u]);
    for (int v : adj[u])
        if (v != p && !used[v])
            reset(v, u, val);
}

void Solve(int c) {
    h[c] = 0;
    up[c] = down[c] = 0;
    L.clear();
    pre(c, 0);
    nodes.clear();
    nodes.pb(c);
    for (int v : adj[c]) 
        if (!used[v]) {
            if (flag) return;
            reset(v, c, -1);
            dfs(v, c);
            reset(v, c, 1);
        }   
    nodes.pop_back();
}

struct Centroid_Decomposition {
    int sz[maxn];
    int dfs(int u, int p) {
        sz[u] = 1;
        for (int v : adj[u])
            if (!used[v] && v != p)
                sz[u] += dfs(v, u);
        return sz[u];
    }
    int Centroid(int u, int p, int tot) {
        for (int v : adj[u])
            if (!used[v] && v != p && sz[v] > tot / 2)
                return Centroid(v, u, tot);
        return u;
    }
    void build(int u) {
        if (flag) return;
        int c = Centroid(u, 0, dfs(u, 0));
        root = c;
        Solve(c);
        used[c] = 1;
        for (int v : adj[c])
            if (!used[v])
                build(v);
    }
} Cen;

bool ok(int m, int sign) {
    flag = false;
    len = 2 * m + sign;
    memset(used, 0, sizeof used);
    Cen.build(1);
    return flag;
}
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    //freopen(".INP", "r", stdin);
    //freopen(".OUT", "w", stdout);
    cin >> n >> s;
    s = ' ' + s;
    for (int i = 1; i < n; i++) {
        int u, v; cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
    Pow[0] = 1;
    for (int i = 1; i <= n; i++) {
        Pow[i] = Pow[i - 1] * base;
    }
    // return cout << ok(2, 1), 0;
    int L = 1, R = n / 2, res = 1;
    while (L <= R) {
        int mid = (L + R) / 2;
        if (ok(mid, 1)) {
            res = 2 * mid + 1;
            L = mid + 1;
        }
        else R = mid - 1;
    }
    L = 1, R = n / 2;
    while (L <= R) {
        int mid = (L + R) / 2;
        if (ok(mid, 0)) {
            res = max(res, 2 * mid);
            L = mid + 1;
        }
        else R = mid - 1;
    }
    cout << res;
}

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