Submission #1248883

#	Time	Username	Problem	Language	Result	Execution time	Memory
1248883		hainam2k9	Lampice (COCI19_lampice)	C++20	17 / 110	5093 ms	9648 KiB

lampice

#include <bits/stdc++.h>
#define tt cin.tie(0), cout.tie(0), ios_base::sync_with_stdio(0)
#define fo freopen((NAME+".INP").c_str(), "r", stdin), freopen((NAME+".OUT").c_str(), "w", stdout)
#define ll long long
#define ull unsigned long long
#define i128 __int128
#define db long double
#define sz(a) ((int)(a).size())
#define pb emplace_back
#define pf emplace_front
#define pob pop_back
#define pof pop_front
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define ins emplace
#define mp make_pair
using namespace std;
const int MOD = 1e9+7, MAXN = 5e4+5, base = 137;
const string NAME = "";
int n,a[MAXN],sz[MAXN];
ll hsh1[MAXN],hsh2[MAXN],basepow[MAXN]={1};
bool del[MAXN],ok;
vector<int> adj[MAXN],vertices;
vector<pair<int,bool>> upd;
unordered_map<int,bool> need,vis;
void GetSize(int u, int par){
    sz[u]=1;
    for(int& v : adj[u])
        if(v!=par&&!del[v]) GetSize(v,u), sz[u]+=sz[v];
}
int Centroid(int u, int par, const int SZ){
    for(int& v : adj[u])
        if(v!=par&&!del[v]&&sz[v]>SZ) return Centroid(v,u,SZ);
    return u;
}
void dfs(int u, int par, const int len){
    vertices.pb(u);
    hsh1[sz(vertices)-1]=(hsh1[sz(vertices)-2]*base+a[u])%MOD,
    hsh2[sz(vertices)-1]=(a[u]*basepow[sz(vertices)-1]+hsh2[sz(vertices)-2])%MOD;
    if(!ok){
        if(sz(vertices)>=(len+1)/2){
            int pos=sz(vertices)-(len+1)/2-1, Start=sz(vertices)-len/2;
            bool check=(pos<0);
            if(pos>=0&&hsh2[pos]==(hsh1[Start+pos]-hsh1[Start-1]*basepow[pos+1]+1ll*MOD*MOD)%MOD) check=1, Start+=pos+1;
            if(Start>=sz(vertices)) ok=1;
            else if(Start<sz(vertices)&&check){
                int val=(hsh1[sz(vertices)-1]-hsh1[Start-1]*basepow[sz(vertices)-Start]+1ll*MOD*MOD)%MOD;
                ok|=vis[val], upd.pb(val,0);
            }
        }
        if(sz(vertices)<=len/2+1){
            int val=(hsh1[sz(vertices)-1]-hsh1[0]*basepow[sz(vertices)-1]+1ll*MOD*MOD)%MOD;
            ok|=need[val], upd.pb(val,1);
        }
    }
    if(sz(vertices)<len)
        for(int& v : adj[u])
            if(v!=par&&!del[v]&&!ok) dfs(v,u,len);
    vertices.pob();
}
bool CentroidDecompostion(int u, const int len){
    GetSize(u,0);
    int root=Centroid(u,0,sz[u]>>1);
    hsh1[0]=hsh2[0]=a[root];
    vertices.pb(u), need.clear(), vis.clear(), ok=0;
    for(int& v : adj[root])
        if(!del[v]&&!ok){
            dfs(v,root,len);
            while(!upd.empty()){
                if(upd.back().se==0) need[upd.back().fi]=1;
                else vis[upd.back().fi]=1;
                upd.pob();
            }
        }
    vertices.pob(), del[root]=1;
    if(ok) return 1;
    for(int& v : adj[root])
        if(!del[v]&&CentroidDecompostion(v,len)) return 1;
    return 0;
}
inline int bs(int l, int r, int odd){
    int rs=1;
    while(l<=r){
        int mid=(l+r)>>1;
        memset(del,0,sizeof(del));
        if(CentroidDecompostion(1,mid*2+odd)) rs=mid*2+odd, l=mid+1;
        else r=mid-1;
    }
    return rs;
}
int main()
{
    tt;
    if(fopen((NAME + ".INP").c_str(), "r")) fo;
    cin >> n;
    for(int i = 1; i<=n; ++i)
        basepow[i]=basepow[i-1]*base%MOD;
    for(int i = 1; i<=n; ++i){
        char c;
        cin >> c;
        a[i]=c-'a'+1;
    }
    for(int i = 1; i<n; ++i){
        int x,y;
        cin >> x >> y;
        adj[x].pb(y), adj[y].pb(x);
    }
    cout << max(bs(1,n/2,0),bs(1,(n-1)/2,1));
}

Compilation message (stderr)

lampice.cpp: In function 'int main()':
lampice.cpp:3:19: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    3 | #define fo freopen((NAME+".INP").c_str(), "r", stdin), freopen((NAME+".OUT").c_str(), "w", stdout)
      |            ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:96:45: note: in expansion of macro 'fo'
   96 |     if(fopen((NAME + ".INP").c_str(), "r")) fo;
      |                                             ^~
lampice.cpp:3:63: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    3 | #define fo freopen((NAME+".INP").c_str(), "r", stdin), freopen((NAME+".OUT").c_str(), "w", stdout)
      |                                                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:96:45: note: in expansion of macro 'fo'
   96 |     if(fopen((NAME + ".INP").c_str(), "r")) fo;
      |                                             ^~

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