[JZOJ4439]不是回文串

题目大意

题目分析

代码实现

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

using namespace std;

const int N=1000500;
const int S=N<<1;
const int C=26;

char s
;

struct Node
{
int prt,len,size;
int next[C];
}sam[S];

int tot,suf,ans;

int insert(int last,int c)
{
int np=++tot,p=last,q;
sam[np].size=1;
for (sam[np].len=sam[p].len+1;p&&!sam[p].next[c];p=sam[p].prt)
sam[p].next[c]=np;
if (!p) sam[np].prt=1;
else
if (sam[p].len+1==sam[q=sam[p].next[c]].len)
sam[np].prt=q;
else
{
int nq=++tot;
sam[nq]=sam[q],sam[nq].size=0,sam[nq].len=sam[p].len+1;
sam[q].prt=sam[np].prt=nq;
for (;p&&sam[p].next[c]==q;p=sam[p].prt)
sam[p].next[c]=nq;
}
return np;
}

int id[S];

bool cmp(int x,int y)
{
return sam[x].len<sam[y].len;
}

void calc()
{
for (int i=1;i<=tot;i++)
id[i]=i;
sort(id+1,id+1+tot,cmp);
for (int i=tot;i>=1;i--)
if (sam[id[i]].prt)
sam[sam[id[i]].prt].size+=sam[id[i]].size;
for (int x=tot;x>=1;x--)
if (sam[x].size>1)
ans=max(ans,sam[x].size*sam[x].len);
}

int n;

int main()
{
freopen("sam.in","r",stdin);
freopen("sam.out","w",stdout);
memset(sam,0,sizeof sam);
tot=suf=1;
scanf("%s",s);
n=strlen(s);
for (int i=0;i<n;i++)
suf=insert(suf,s[i]-'a');
calc();
printf("%d\n",ans);
fclose(stdin);
fclose(stdout);
return 0;
}