poj 1743 Musical Theme(SAM解法)

//poj 1743 Musical Theme
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#define inf 1e9+7
#define ll long long
#define M(a) memset(a,0,sizeof a)
#define fo(i,j,k) for(i=j;i<=k;i++)
using namespace std;
const int mxn=40005;
int n,m,p,q,np,nq,tot,len,ans,root;
int a[mxn],s[mxn],b[mxn],t[mxn],mx[mxn],mn[mxn];
int son[mxn][180],step[mxn],pre[mxn];
inline void sam()
{
int i,j;
M(son),M(b);
memset(mx,0,sizeof mx);
memset(mn,0x3f,sizeof mn);
fo(i,1,len) scanf("%d",&s[i]);
fo(i,1,len-1) a[i]=s[i+1]-s[i]+88;
len--;
root=tot=np=1;
fo(i,1,len)
{
int c=a[i];
p=np;
step[np=(++tot)]=step[p]+1;
while(p && !son[p][c])
son[p][c]=np,p=pre[p];
if(!p)
{
pre[np]=root;
continue;
}
q=son[p][c];
if(step[q]==step[p]+1)
pre[np]=q;
else
{
step[nq=(++tot)]=step[p]+1;
memcpy(son[nq],son[q],sizeof son[q]);
pre[nq]=pre[q];
pre[np]=pre[q]=nq;
while(p && son[p][c]==q)
son[p][c]=nq,p=pre[p];
}
}

}
int main()
{
int i,j;
while(scanf("%d",&len) && len)
{
ans=0;
sam();
fo(i,1,tot) b[step[i]]++;
fo(i,1,len) b[i]+=b[i-1];
fo(i,1,tot) t[b[step[i]]--]=i;
p=1;
fo(i,1,len)
{
p=son[p][a[i]];
mn[p]=mx[p]=i;
}
for(i=tot;i>=1;i--)
{
int now=t[i],fa=pre[now];
ans=max(ans,min(mx[now]-mn[now]-1,step[now]));
mx[fa]=max(mx[fa],mx[now]);
mn[fa]=min(mn[fa],mn[now]);
}
ans++;
if(ans<=4) ans=0;
printf("%d\n",ans);
}
return 0;
}