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ACM ICPC 2018 World Finals

## RT

Posted by 2730052770 at 2017-12-04 19:06:31 on Problem 1743
```#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#define N 20005
using namespace std;
int s[N],sa[N],rk[N],ht[N],c[N],a[2][N],mx[20][N],mn[20][N],lg[N];
void build(int n,int m)
{
int i,k,p,*x=a[0],*y=a[1];
for(i=0;i<m;i++)c[i]=0;
for(i=0;i<n;i++)c[x[i]=s[i]]++;
for(i=1;i<m;i++)c[i]+=c[i-1];
for(i=n-1;i>=0;i--)sa[--c[x[i]]]=i;
for(k=1;k<=n;k<<=1){
p=0;
for(i=n-k;i<n;i++)y[p++]=i;
for(i=0;i<n;i++)if(sa[i]>=k)y[p++]=sa[i]-k;
for(i=0;i<m;i++)c[i]=0;
for(i=0;i<n;i++)c[x[i]]++;
for(i=1;i<m;i++)c[i]+=c[i-1];
for(i=n-1;i>=0;i--)sa[--c[x[y[i]]]]=y[i];
swap(x,y);
m=1,x[sa[0]]=0,y[n]=-1;
for(i=1;i<n;i++)
x[sa[i]]=y[sa[i]]==y[sa[i-1]]&&y[sa[i]+k]==y[sa[i-1]+k]?m-1:m++;
if(m>=n)break;
}
memcpy(rk,x,sizeof(rk));
k=0,ht[0]=0;
for(i=0;i<n;i++){
if(k)k--;
if(!rk[i])continue;
int j=sa[rk[i]-1];
while(s[i+k]==s[j+k]&&i+k<n&&j+k<n)k++;
ht[rk[i]]=k;
}
}
void ST(int n){
memcpy(mx[0],sa,sizeof(sa));
memcpy(mn[0],sa,sizeof(sa));
for(int i=1;i<20;i++)
for(int j=0;j+(1<<i)-1<n;j++)
mx[i][j]=max(mx[i-1][j],mx[i-1][j+(1<<(i-1))]),
mn[i][j]=min(mn[i-1][j],mn[i-1][j+(1<<(i-1))]);
for(int i=2;i<N;i++)lg[i]=lg[i>>1]+1;
}
bool query(int l,int r,int lmt){
int Lg=lg[r-l+1],len=1<<Lg;
return max(mx[Lg][l],mx[Lg][r-len+1])-min(mn[Lg][l],mn[Lg][r-len+1])>=lmt;
}
bool check(int mid,int n){
int pre=0;
ht[n]=0x80000000;
for(int i=1;i<=n;i++)if(ht[i]<mid){
if(query(pre,i-1,mid+1))return 1;//×¢ÒâÊÇmid+1ÒòÎªÒªÇó²»ÖØ¸´
pre=i;//Ôò²îÖµÊý×é(¼´sÊý×é)ÖÐµÄÁ½¶ÎÓ¦¸ÃÊÇÖÁÉÙ¸ôÁËÒ»¸öÊýµÄ
}//¶ø²»ÄÜ½ôÌù×Å,½ôÌù×ÅµÄ»°Ô­Êý×é¾Í»áÓÐÖØ¸´
return 0;
}
int main()
{
int n;
while(cin>>n&&n)
{
for(int i=0;i<n;i++)scanf("%d",&s[i]);
for(int i=n-1;i>=1;i--)s[i]-=s[i-1];
n--;
for(int i=0;i<n;i++)s[i]=s[i+1]+100;
s[n]=0;
build(n,200);
//for(int i=0;i<n;i++)printf("%d %d %d\n",s[i],sa[rk[i]],ht[i]);
ST(n);
int l=4,r=n,mid,ans=-1;
while(l<=r){
mid=(l+r)>>1;
if(check(mid,n)) ans=mid,l=mid+1;
else r=mid-1;
}
cout<<ans+1<<endl;
}
return 0;
}```

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