poj1743

#include<cstdio>
#include<cstring>
#include<algorithm>
#define MN 20003
using namespace std;

int n;
char s1[MN];
int s[MN],a[MN];
int v[MN],sa[MN],q[MN],rank[MN],h[MN],mmh=0,len;
inline void gr(int x){
    rank[sa[1]]=1;
    for (int i=2;i<=n;i++) rank[sa[i]]=(s[sa[i]]==s[sa[i-1]]&&s[sa[i]+x]==s[sa[i-1]+x])?rank[sa[i-1]]:rank[sa[i-1]]+1;
    for (int i=1;i<=n;i++) s[i]=rank[i];
}
inline void gv(){memset(v,0,sizeof(v));for (int i=1;i<=n;i++) v[s[i]]++;for (int i=1;i<=2e4;i++)v[i]+=v[i-1];}
inline void gsa(){
    gv();for (int i=n;i>=1;i--) sa[v[s[i]]--]=i;gr(0);
    for (int i=1;i<n;i<<=1){
        gv();for (int j=n;j>=1;j--) if (sa[j]>i) q[v[s[sa[j]-i]]--]=sa[j]-i;
        for (int j=n-i+1;j<=n;j++) q[v[s[j]]--]=j;
        for (int j=1;j<=n;j++) sa[j]=q[j];gr(i);
        if (rank[sa[n]]==n) return;
    }
}
inline void gh(){for (int i=1,k=0,j;i<=n;h[rank[i++]]=k) for (k?k--:0,j=sa[rank[i]-1];a[i+k]==a[j+k]&&i+k<=n&&j+k<=n;k++);}
int main(){
    scanf("%d",&n);
    while(n){
        for (int i=1;i<=n;i++) scanf("%d",&a[i]);
        if(n<10){printf("0\n");scanf("%d",&n);continue;}
        n--;
        for (int i=1;i<=n;i++) s[i]=a[i+1]-a[i]+90;s[n+1]=0;
        for (int i=1;i<=n;i++) a[i]=s[i];
        gsa();gh();
        int l=4,r=2e4,mid,bo=1,ma,mi,i,j,k;
        while(l<r){
            mid=(l+r+1)>>1;
            for (i=1,j,k=2;i<=n;i=k++){
                ma=0;mi=2e4;
                while (h[k]>=mid&&k<=n) k++;
                for (j=i;j<k;j++){
                    if (ma<sa[j]) ma=sa[j];
                    if (mi>sa[j]) mi=sa[j];
                }
                if (ma-mi>=mid) break;
            }
            if (i>n) r=mid-1;else l=mid;
        }
        l=l<4?0:l+1;
        printf("%d\n",l);
        scanf("%d",&n);
    }
}