//Name: Nguyen Quang Huy
//Time: 2023-2024
#include <bits/stdc++.h>
#define Foru(i,a,b) for(int i=(a);i<=(b);++i)
#define Ford(i,a,b) for(int i=(a);i>=(b);--i)
#define se second
#define fi first
#define nl cout << "\n";
#define pi pair<int,int>
#define bit(x, k) (1ll&((x)>>(k)))
//#define sz size
#define io() ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define ms(a,i) memset(a,i,sizeof(a))
#define pb(x) push_back(x)
#define epb(x,y) emplace_back({x,y})
#define all(x) (x).begin(), (x).end()
#define hr cout << "-----------------------------------------------\n";
typedef long long ll;
using namespace std;
const ll mod=1e9+7;
const int inf=0x3f3f3f3f;
const long long base=311;
const int maxn=5e4+7;
template<class T> T mi(T a, T b){return (a<=b)?a:b;}
template<class T> T ma(T a, T b){return (a>=b)?a:b;}
template<class T> void Unique(vector<T> &v){sort(all(v));v.erase(unique(all(v)), v.end());}
int n;
vector<int> g[maxn];
int sz[maxn], mxd=1, Len, ans, cc;
char a[maxn];
ll pw[maxn];
bool del[maxn], found;
unordered_map<ll,bool> mp[maxn];
void ioFile(string str){
freopen((str+".in").c_str(),"r",stdin);
freopen((str+".out").c_str(),"w",stdout);
}
void inp(){
cin >> n;
Foru(i,1,n)cin >> a[i];
Foru(i,1,n-1){
int u,v;cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
pw[0]=1;
Foru(i,1,maxn) pw[i]=(1ll*pw[i-1]*base)%mod;
}
void dfsBase(int u,int p){
sz[u]=1;
for(int v:g[u])if(v!=p&&!del[v]){
dfsBase(v,u);
sz[u]+=sz[v];
}
}
int centroid(int u, int p, int d){
for(int v:g[u])if(v!=p&&sz[v]>d&&!del[v]){
return centroid(v,u,d);
}
return u;
}
bool dfs(int u, int p, int h, ll hd, ll hu, bool t){
hd=(hd*1ll*base+(a[u]-'a'+1))&mod;
hu=(hu+pw[h-1]*1ll*(a[u]-'a'+1))%mod;
ll x=(hu*1ll*pw[Len-h]-hd+mod)%mod;
if(t){
if(h+1==Len&&((hu*1ll*base+(a[cc]-'a'+1))%mod==hd)){
return true;
}
if(Len>h&&mp[Len-h-1].find(x)!=mp[Len-h-1].end()){
return true;
}
} else {mp[h][x]=true;}
if(Len>h){
for(int v:g[u])if(v!=p&&!del[v]){
mxd=max(mxd,h+1);
if(dfs(v,u,h+1,hd,hu,t))return true;
}
}
return false;
}
bool cd(int u=1){
dfsBase(u,0);
int r=centroid(u,0,sz[u]/2);
cc=r;
del[r]=true;
mxd=1;
for(int v:g[r])if(!del[v]){
if(dfs(v,0,1,(a[r]-'a'+1),0,true))return true;
if(dfs(v,0,1,(a[r]-'a'+1),0,false))return true;
}
Foru(i,0,mxd)mp[i].clear();
for(int v:g[r])if(!del[v]){
if(cd(v))return true;
}
return false;
}
bool ok(int len){
Foru(i,0,n)mp[i].clear();
ms(del,false);
found=false;
Len=len;
return cd();
}
void solve(){
vector<int> le,chan;
le.pb(1);chan.pb(2);
Foru(i,1,n){
if(i&1)le.pb(i);
else chan.pb(i);
}
int l=1,r=le.size()-1,mid;
while(l<r){
mid=(l+r)/2;
if(ok(le[mid]))l=mid;
else r=mid-1;
}
ans=le[l];
l=1,r=chan.size()-1;
while(l<r){
mid=(l+r)/2;
if(ok(chan[mid]))l=mid;
else r=mid-1;
}
cout << max(chan[l],ans);
}
int main(){
io();
inp();
solve();
return 0;
}
Compilation message
lampice.cpp: In function 'void ioFile(std::string)':
lampice.cpp:40:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
40 | freopen((str+".in").c_str(),"r",stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:41:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
41 | freopen((str+".out").c_str(),"w",stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp: In function 'void inp()':
lampice.cpp:53:25: warning: iteration 50006 invokes undefined behavior [-Waggressive-loop-optimizations]
53 | Foru(i,1,maxn) pw[i]=(1ll*pw[i-1]*base)%mod;
| ~~~~~^~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:4:36: note: within this loop
4 | #define Foru(i,a,b) for(int i=(a);i<=(b);++i)
| ^
lampice.cpp:53:5: note: in expansion of macro 'Foru'
53 | Foru(i,1,maxn) pw[i]=(1ll*pw[i-1]*base)%mod;
| ^~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5012 ms |
5208 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5045 ms |
14172 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1404 ms |
10852 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5012 ms |
5208 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
