| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 168063 | HungAnhGoldIBO2020 | Palindromes (APIO14_palindrome) | C++14 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
/*
abacaba
*/
#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=3e5+2;
const int mod=1e9+9;
const int base=79;
int hash[N],rev_hash[N],mul[N],max1=0,sum[N];
map<int,int> cnt;
int gethash(int l,int r){
return ((hash[r]-hash[l-1]*mul[r-l+1])%mod+mod)%mod;
}
int gethash_rev(int l,int r){
return ((rev_hash[l]-rev_hash[r+1]*mul[r-l+1])%mod+mod)%mod;
}
struct node{
int nxt[26],len,suf;
};
node Eer[N];
int sz=0,lst;
string s;
void add(int idx){
// cout<<idx<<" BEGIN"<<endl;
//special case idx=0
int cha=(s[idx]-'a');
if(idx==0){
sz++;
Eer[1].nxt[cha]=sz;
Eer[sz].len=1;
Eer[sz].suf=2;
return;
}
while(idx-Eer[lst].len-1<=0||s[idx]!=s[idx-Eer[lst].len-1]){
if(lst==1){
break;
}
lst=Eer[lst].suf;
}
if(!Eer[lst].nxt[cha]){
sz++;
Eer[lst].nxt[cha]=sz;
Eer[sz].len=Eer[lst].len+2;
if(Eer[sz].len!=1){
int sf=Eer[lst].suf;
assert(idx-Eer[sf].len-1>0);
while(s[idx]!=s[idx-Eer[sf].len-1]){
sf=Eer[sf].suf;
}
Eer[sz].suf=Eer[sf].nxt[cha];
}
else{
Eer[sz].suf=2;
}
}
lst=Eer[lst].nxt[cha];
// cout<<"LST "<<lst<<" LEN "<<Eer[lst].len<<" SUF "<<Eer[sz].suf<<endl;
// cout<<"END"<<endl;
return;
}
void build(string s1){
sz=2;
Eer[1].len=-1;
Eer[1].suf=1;
Eer[2].len=0;
Eer[2].suf=1;
lst=1;
s=s1;
for(int i=0;i<s.size();i++){
add(i);
}
}
void dfs(int x,int val){
sum[x]=cnt[val];
for(int i=0;i<26;i++){
if(Eer[x].nxt[i]){
if(Eer[x].len==-1){
dfs(Eer[x].nxt[i],i+1);
}
else{
dfs(Eer[x].nxt[i],(i+1 + val*base + (i+1)*mul[Eer[x].len+1])%mod);
}
sum[x]+=sum[Eer[x].nxt[i]];
}
}
max1=max(max1,Eer[x].len*sum[x]);
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
string s1;
cin>>s1;
build(s1);
int n=s1.size(),i,j,k,l,z;
s1=" "+s1;
mul[0]=1;
for(i=1;i<=n;i++){
hash[i]=(hash[i-1]*base+(s1[i]-'a'+1))%mod;
mul[i]=(mul[i-1]*base)%mod;
}
for(i=n;i>0;i--){
rev_hash[i]=(rev_hash[i+1]*base+(s1[i]-'a'+1))%mod;
}
for(i=1;i<=n;i++){
k=0;
l=min(i-1,n-i);
while(k<l){
j=(k+l+1)>>1;
if(gethash(i-j,i+j)==gethash_rev(i-j,i+j)){
k=j;
}
else{
l=j-1;
}
}
cnt[gethash(i-k,i+k)]++;
if(i<=n&&s1[i]==s1[i+1]){
k=0;
l=min(i-1,n-i-1);
while(k<l){
j=(k+l)/2;
if(gethash(i-j,i+1+j)==gethash_rev(i-j,i+1+j)){
k=j;
}
else{
l=j-1;
}
}
cnt[gethash(i-k,i+1+k)]++;
}
}
dfs(1,0);
dfs(2,0);
for(i=1;i<=n;i++){
if(gethash(1,i)==gethash_rev(1,i)){
max1=max(max1,i);
}
}
cout<<max1;
}