제출 #923000

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
923000		ttamx	Lampice (COCI19_lampice)	C++14	25 / 110	4264 ms	26844 KiB

lampice

#include<bits/stdc++.h>

using namespace std;

using ull = unsigned long long;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

const int N=5e5+5;
const ull BASE=rng();

int n;
string s;
int a[N];
vector<int> adj[N];
ull hsh[26],pw[N],hsh2[N];
int sz[N];
bool used[N];
int len;
map<ull,bool> mp;

void init(){
    for(int i=1;i<=n;i++)used[i]=false;
}

int get_sz(int u,int p=0){
    sz[u]=1;
    for(auto v:adj[u])if(v!=p&&!used[v])sz[u]+=get_sz(v,u);
    return sz[u];
}

int centroid(int u,int cnt,int p=0){
    for(auto v:adj[u])if(v!=p&&!used[v]&&sz[v]>cnt/2)return centroid(v,cnt,u);
    return u;
}

bool dfs1(int u,int p,ull cur,ull rev,int sz){
    if(sz>len)return false;
    if(mp[(rev*pw[len-sz]-cur)*hsh2[len-sz]])return true;
    for(auto v:adj[u])if(v!=p&&!used[v]){
        if(dfs1(v,u,cur*BASE+a[v],rev+a[v]*pw[sz],sz+1)){
            return true;
        }
    }
    return false;
}

void dfs2(int u,int p,ull cur,ull rev,int sz){
    if(sz>len)return;
    mp[(rev*pw[len-sz]-cur)*hsh2[sz]]=true;
    for(auto v:adj[u])if(v!=p&&!used[v]){
        dfs2(v,u,cur*BASE+a[v],rev+a[v]*pw[sz],sz+1);
    }
}

bool decom(int u){
    u=centroid(u,get_sz(u));
    used[u]=true;
    mp.clear();
    for(auto v:adj[u])if(!used[v]){
        if(dfs1(v,u,a[v],a[v],1))return true;
        dfs2(v,u,a[u]*BASE+a[v],a[v]*BASE+a[u],2);
    }
    for(auto v:adj[u])if(!used[v]&&decom(v))return true;
    return false;
}

int solve1(){
    int l=0,r=(n-1)/2;
    while(l<r){
        int m=(l+r+1)/2;
        len=m*2+1;
        init();
        if(decom(1))l=m;
        else r=m-1;
    }
    return l*2+1;
}

int solve2(){
    int l=0,r=n/2;
    while(l<r){
        int m=(l+r+1)/2;
        len=m*2;
        init();
        if(decom(1))l=m;
        else r=m-1;
    }
    return l*2;
}

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    for(int i=0;i<26;i++)hsh[i]=rng();
    cin >> n >> s;
    pw[0]=1;
    for(int i=1;i<=n;i++)pw[i]=pw[i-1]*BASE;
    for(int i=1;i<=n;i++)a[i]=hsh[s[i-1]-'a'];
    for(int i=0;i<=n;i++)hsh2[i]=rng();
    for(int i=1;i<n;i++){
        int u,v;
        cin >> u >> v;
        adj[u].emplace_back(v);
        adj[v].emplace_back(u);
    }
    cout << max(solve1(),solve2());
}

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