[字典树上建回文自动机] ICPC Preparatory Series by Team Akatsuki. Three Palindromes

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

const int N=100010;

int n,cnt,tot,fail[N],len[N],p[N],G[N],nxt[N][30],trans[N][30];
int a
,s
;
struct edge{
int t,nx;
}E[N<<1];

inline void addedge(int x,int y){
E[++cnt].t=y; E[cnt].nx=G[x]; G[x]=cnt;
E[++cnt].t=x; E[cnt].nx=G[y]; G[y]=cnt;
}

inline int extend(int x,int p){
if(x!=s[tot-len[p]-1]) p=trans[p][x];
if(!nxt[p][x]){
int cur=++cnt,k=fail[p]; len[cur]=len[p]+2;
if(x!=s[tot-len[k]-1]) k=trans[k][x];
fail[cur]=nxt[k][x];
memcpy(trans[cur],trans[fail[cur]],sizeof(trans[cur]));
trans[cur][s[tot-len[fail[cur]]]]=fail[cur];
nxt[p][x]=cur;
}
return nxt[p][x];
}

long long ans=0;
int ians[N];

void dfs(int x,int f){
s[++tot]=a[x];
p[x]=extend(a[x],p[f]);
ians[x]=max(len[p[x]],ians[f]);
ans+=ians[x];
//printf("%d %d\n",x,len[p[x]]);
for(int i=G[x];i;i=E[i].nx)
if(E[i].t!=f) dfs(E[i].t,x);
tot--;
}

int main(){
freopen("1.in","r",stdin);
freopen("1.out","w",stdout);
scanf("%d",&n); s[0]=-1;
for(int i=1;i<=n;i++) while((a[i]=getchar()-'a')<0 || a[i]>25);
for(int i=1,x,y;i<n;i++)
scanf("%d%d",&x,&y),addedge(x,y);
cnt=1; fail[0]=fail[1]=1; len[1]=-1;
for(int i=0;i<26;i++) trans[0][i]=1;
dfs(1,0);
cout<<ans<<endl;
return 0;
}