Submission #1281956

#	Time	Username	Problem	Language	Result	Execution time	Memory
1281956		quan606303	Lampice (COCI19_lampice)	C++20	110 / 110	2076 ms	15784 KiB

lampice

/*
 * @Author: RMQuan 
 * @Date: 2025-10-22 
 * @Last Modified by: RMQuan
 * @Last Modified time: 2025-10-22 17:30:00
 */
#include <bits/stdc++.h>
bool M1;
#define int long long
#define ll long long
#define fi first
#define se second
#define endl '\n'
#define TASK "LAMPICE"
#define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
#define memfull(a,b) memset(a,b,sizeof(a))
using namespace std;

const int MOD=1e9+7;
const int maxn=50005;
const int base=31;

int n,len,mx;
string S;
vector<int> adj[maxn];
int a[maxn],sz[maxn],pw[maxn];
bool is_deleted[maxn];
unordered_set<int> f[maxn];
vector<pair<int,int> > L;

int addm(int x,int y){x%=MOD;y%=MOD;return (x+y)%MOD;}
int subm(int x,int y){x%=MOD;y%=MOD;return (x-y+MOD)%MOD;}
int mulm(int x,int y){return (x*y)%MOD;}

int dfs_size(int u,int p){
    sz[u]=1;
    for(int v:adj[u]) if(v!=p&&!is_deleted[v])
        sz[u]+=dfs_size(v,u);
    return sz[u];
}
int find_centroid(int u,int p,int tot){
    for(int v:adj[u]) if(v!=p&&!is_deleted[v])
        if(sz[v]>tot/2) return find_centroid(v,u,tot);
    return u;
}

bool dfs_hash(int u,int p,int dep,int down,int up){
    if(dep>len) return 0;
    if(p) down=(down*base+a[u])%MOD;
    up=(up+mulm(a[u],pw[dep-1]))%MOD;
    int x=(mulm(up,pw[len-dep])-down+MOD)%MOD;
    if(!p) f[dep].insert(x);
    if(f[len-dep+1].count(x)) return 1;
    for(int v:adj[u]) if(v!=p&&!is_deleted[v]){
        if(!p) L.clear();
        if(dfs_hash(v,u,dep+1,down,up)) return 1;
        if(!p){
            for(auto l:L) f[l.fi].insert(l.se);
        }
    }
    mx=max(mx,dep);
    L.push_back({dep,x});
    return 0;
}

bool solve_centroid(int u,int par){
    int tot=dfs_size(u,par);
    int c=find_centroid(u,par,tot);
    if(dfs_hash(c,0,1,0,0)) return 1;
    for(int i=1;i<=mx;i++) f[i].clear();
    mx=0;
    is_deleted[c]=1;
    for(int v:adj[c]) if(v!=par&&!is_deleted[v])
        if(solve_centroid(v,c)) return 1;
    return 0;
}

bool check(int mid){
    len=mid;
    for(int i=1;i<=n;i++) is_deleted[i]=0, f[i].clear();
    return solve_centroid(1,0);
}

int32_t main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    file();
    cin>>n>>S; S="$"+S;
    pw[0]=1; for(int i=1;i<=n;i++) pw[i]=mulm(pw[i-1],base);
    for(int i=1;i<=n;i++) a[i]=S[i]-'a'+1;
    for(int i=1;i<n;i++){
        int x,y; cin>>x>>y;
        adj[x].push_back(y); adj[y].push_back(x);
    }

    int lo=-1,hi=n+1,ans=0;
    while(hi-lo>1){
        int mid=(lo+hi)/2;
        if(mid&1){
            if(check(mid)) lo=mid; else hi=mid;
        }else{
            if(check(mid+1)) lo=mid+1; else hi=mid;
        }
    }
    ans=max(ans,lo);
    lo=-1; hi=n+1;
    while(hi-lo>1){
        int mid=(lo+hi)/2;
        if(mid&1){
            if(check(mid+1)) lo=mid+1; else hi=mid;
        }else{
            if(check(mid)) lo=mid; else hi=mid;
        }
    }
    ans=max(ans,lo);
    cout<<ans<<endl;

    bool M2;
    cerr<<"-----------------------------------------------"<<endl;
    cerr<<"Time : "<<clock()<<" ms"<<endl;
    cerr<<"Memory : "<<abs(&M2-&M1)/1024/1024<<" MB"<<endl;
    cerr<<"-----------------------------------------------"<<endl;
    return 0;
}

Compilation message (stderr)

lampice.cpp: In function 'int32_t main()':
lampice.cpp:15:50: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 | #define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
      |                                           ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:87:5: note: in expansion of macro 'file'
   87 |     file();
      |     ^~~~
lampice.cpp:15:81: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 | #define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
      |                                                                          ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:87:5: note: in expansion of macro 'file'
   87 |     file();
      |     ^~~~

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