[Apio2014]回文串

http://www.lydsy.com:808/JudgeOnline/problem.php?id=3676

这是一道回文树裸题，具体如何建图见http://blog.csdn.net/u013368721/article/details/42100363

code：

 #include<cstdio>
 #include<iostream>
 #include<cstring>
 #include<algorithm>
 #define maxn 300005
 using namespace std;
 typedef long long int64;
 char s[maxn];
 struct ptree{
     int n,last,idx,s[maxn],son[maxn][],fai[maxn],len[maxn],cnt[maxn];
     void init(){n=,s[]=-,idx=,last=,fai[]=,len[]=-;}
     int get_fai(int x){
         while (s[n-len[x]-]!=s[n]) x=fai[x];
         return x;
     }
     void insert(int ch){
         s[++n]=ch;
         int p=get_fai(last);
         if (!son[p][ch]){
             len[++idx]=len[p]+;
             int q=idx;
             fai[q]=son[get_fai(fai[p])][ch];
             son[p][ch]=q;
         }
         cnt[last=son[p][ch]]++;
     }
     void count(){for (int i=idx;i>=;i--) cnt[fai[i]]+=cnt[i];}
     void query(){
         int64 ans=;
         count();
         for (int i=;i<=idx;i++) ans=max(ans,1LL*cnt[i]*len[i]);
         printf("%lld\n",ans);
     }
 }T;
 int main(){
     scanf("%s",s+); T.init();
     for (int i=;s[i];i++) T.insert(s[i]-'a');
     T.query();
     return ;
 }