Submission #904316

#	Time	Username	Problem	Language	Result	Execution time	Memory
904316		coldbr3w	Lampice (COCI19_lampice)	C++14	0 / 110	2534 ms	112188 KiB

lampice

#pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pll = pair<long long, long long>;

#define pb push_back
#define F first
#define S second  
#define all(x) (x).begin(), (x).end()
#define int long long
const ll N = 3e5 + 100;
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ll block = 520;
const ll base = 35711;
vector<int>adj[N];
int n, cur_sz; string s;
int sz[N]; bool vs[N];
ll hsh[N], pw[N];
unordered_map<int,int>mp;
int ans = 0;
void get_sz(int u, int par){
    sz[u] = 1;
    for(auto v : adj[u]){
        if(v == par || vs[v]) continue;
        get_sz(v, u);
        sz[u] += sz[v];
    }
}
int find_cen(ll u, ll par){
    for(auto v : adj[u]){
        if(v == par || vs[v]) continue;
        if(sz[v] > cur_sz / 2) return find_cen(v, u);
    }
    return u;
}
int get_cen(ll v){
    get_sz(v, 0);
    cur_sz = sz[v];
    return find_cen(v, 0);
}
void add(ll u, ll par, ll cur){
    cur = ((cur * base) + (s[u] - 'a' + 1)) % mod;
    mp[cur]++;
    for(auto v : adj[u]){
        if(v == par || vs[v]) continue;
        add(v, u, cur);
    }
}
void del(ll u, ll par, ll cur){
    cur = ((cur * base) + (s[u] - 'a' + 1)) % mod;
    mp[cur]--;
    for(auto v : adj[u]){
        if(v == par || vs[v]) continue;
        del(v, u, cur);
    }
}
int get_hash(int l, int r){
    return (hsh[r] - hsh[l - 1] * pw[r - l + 1] + mod * mod) % mod;
}
bool dfs(int u, int par, int d, int len, ll cur){
    cur = ((cur * base) + (s[u] - 'a' + 1)) % mod;
    if(d > len) return 0;
    hsh[d] = ((hsh[d-1] * base) + (s[u] - 'a' + 1)) % mod;
    if(d >= len / 2 + len % 2){
        ll r = d, l = (d - (len - d) + 1);
        ll tmp = get_hash(l, r);
        if(mp[tmp]) return 1;
    }
    if(d == len / 2){
        if(mp[cur]) return 1;
    }
    for(auto v : adj[u]){
        if(v == par || vs[v]) continue;
        if(dfs(v, u, d + 1, len, cur)) return 1;
    }
    return 0;
}
void centroid(ll u){
    vs[u] = 1;
    int l = 0, r = n + 1;   
    add(u, 0, 0);
    while(l + 1 < r){
        int mid = (l + r) / 2;
        bool ck = 0;
        for(auto v : adj[u]){
            if(vs[v]) continue;
            del(v, u, (s[u] - 'a' + 1));
            if(mid + 1 <= min(n, r)){
                if(dfs(v, u, 1, mid + 1, (s[u] - 'a' + 1))){
                    ck = 1;
                    l = mid + 1;
                }
            }
            if(mid <= min(n, r) && !ck){
                if(dfs(v, u, 1, mid, (s[u] - 'a' + 1))){
                    ck = 1;
                    l = mid;
                }
            }
            add(v, u, (s[u] - 'a' + 1));
            if(ck) break;
        }
        if(!ck) r = mid;
    }
    ans = max(ans, l);
    for(auto v : adj[u]){
        if(vs[v]) continue;
        ll nxt = get_cen(v);
        centroid(nxt);
    }
}
void to_nho_cau(){
    cin >> n >> s;
    s = " " + s;
    pw[0] = 1;
    for(int i = 1; i <= n + 1;i++) pw[i] = (pw[i-1] * base) % mod;
    for(int i = 1; i <= n - 1;i++){
        ll u,v; cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
    ll root = get_cen(1);
    centroid(root);
    cout << ans << '\n';
}

signed main()
{   
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int t = 1;   
    //cin >> t;
    while(t--) to_nho_cau();
}

• Subtask 1: 0 / 17
• Subtask 2: 0 / 25
• Subtask 3: 0 / 31
• Subtask 4: 0 / 37