#include<bits/stdc++.h> using namespace std; typedef long long ll; #define fi first #define se second const int N=3e5+5; int n; string s; int f[226]; int sz=1; const int ts=6e5+5; int ch[ts][26]; int fa[ts],len[ts]; int mp[ts]; int king[N]; vector<int>adj[ts]; int rsz[ts]; int fi[ts],pl[ts]; void dfs(int id){ for(auto c:adj[id]){ dfs(c); rsz[id]+=rsz[c]; } } void dfs2(int id){ for(auto c:adj[id]){ dfs2(c); if(fi[c]!=0){ int i=fi[c]; int cl=len[id]; int x=id; if(i+cl-1>=mp[x]){ if(mp[x]-i+1>len[fa[x]]){ pl[x]=mp[x]-i+1; } } fi[id]=max(fi[id],fi[c]); } } } int main(){ ios::sync_with_stdio(false); for(int i='a'; i<='z' ;i++) f[i]=i-'a'; cin >> s;n=s.size();s='?'+s; int x=1; for(int i=1; i<=n ;i++){ char c=s[i]; int y=++sz;len[y]=i; while(x && !ch[x][f[c]]){ ch[x][f[c]]=y; x=fa[x]; } if(!x){ fa[y]=1; } else if(len[x]+1==len[ch[x][f[c]]]){ fa[y]=ch[x][f[c]]; } else{ int w=ch[x][f[c]]; int z=++sz;len[z]=len[x]+1; for(int j=0; j<26 ;j++) ch[z][j]=ch[w][j]; fa[z]=fa[w];fa[w]=z; while(ch[x][f[c]]==w){ ch[x][f[c]]=z; x=fa[x]; } fa[y]=z; } king[i]=x=y; } for(int i=2; i<=ts ;i++){ adj[fa[i]].push_back(i); } for(int i=n; i>=1 ;i--){ int x=king[i]; while(!mp[x]){ mp[x]=i;x=fa[x]; } rsz[king[i]]++; } dfs(1); x=1; int cl=0; for(int i=n; i>=1 ;i--){ char c=s[i]; while(ch[x][f[c]]==0){ x=fa[x]; cl=len[x]; } x=ch[x][f[c]]; cl++; if(fi[x]==0) fi[x]=i; if(i+cl-1>=mp[x]){ if(mp[x]-i+1>len[fa[x]]){ pl[x]=mp[x]-i+1; } } } dfs2(1); ll ans=0; for(int i=1; i<=sz ;i++){ //cout << pl[i] << '\n'; if(pl[i]!=0) ans=max(ans,1LL*pl[i]*rsz[i]); } cout << ans << '\n'; }

palindrome.cpp: In function 'int main()':
palindrome.cpp:51:23: warning: array subscript has type 'char' [-Wchar-subscripts]
   51 |   while(x && !ch[x][f[c]]){
      |                       ^
palindrome.cpp:52:12: warning: array subscript has type 'char' [-Wchar-subscripts]
   52 |    ch[x][f[c]]=y;
      |            ^
palindrome.cpp:58:33: warning: array subscript has type 'char' [-Wchar-subscripts]
   58 |   else if(len[x]+1==len[ch[x][f[c]]]){
      |                                 ^
palindrome.cpp:59:18: warning: array subscript has type 'char' [-Wchar-subscripts]
   59 |    fa[y]=ch[x][f[c]];
      |                  ^
palindrome.cpp:62:18: warning: array subscript has type 'char' [-Wchar-subscripts]
   62 |    int w=ch[x][f[c]];
      |                  ^
palindrome.cpp:66:18: warning: array subscript has type 'char' [-Wchar-subscripts]
   66 |    while(ch[x][f[c]]==w){
      |                  ^
palindrome.cpp:67:13: warning: array subscript has type 'char' [-Wchar-subscripts]
   67 |     ch[x][f[c]]=z;
      |             ^
palindrome.cpp:89:17: warning: array subscript has type 'char' [-Wchar-subscripts]
   89 |   while(ch[x][f[c]]==0){
      |                 ^
palindrome.cpp:93:13: warning: array subscript has type 'char' [-Wchar-subscripts]
   93 |   x=ch[x][f[c]];
      |             ^