记录编号	216927	评测结果	AAAAAAAAAAAAAAA
题目名称	乐曲主题	最终得分	100
用户昵称	一個人的雨	是否通过	通过
代码语言	C++	运行时间	0.010 s
提交时间	2016-01-01 16:22:22	内存使用	3.37 MiB

#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<cstdio>
#include<vector>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn=100000+10;
int n,Ws[maxn],wv[maxn],wa[maxn],wb[maxn];
int a[maxn],height[maxn],sa[maxn],rank[maxn];
char ch;
int read(){
	int num=0; ch=getchar();
	while (ch<'!') ch=getchar();
    while (ch>='0'&&ch<='9'){num=num*10+ch-'0';ch=getchar();}
	return num;
}

bool cmp(int *r,int a,int b,int l){
	return r[a]==r[b]&&r[a+l]==r[b+l];
}

void da(int *r,int *sa,int n,int m){
	int i,j,p,*x=wa,*y=wb,*t;
	for (i=0;i<m;++i) Ws[i]=0;
	for (i=0;i<n;++i) Ws[x[i]=r[i]]++;
	for (i=1;i<m;++i) Ws[i]+=Ws[i-1];
	for (i=n-1;i>=0;--i) sa[--Ws[x[i]]]=i;
	for (j=1,p=1;p<n;j<<=1,m=p){
		for (p=0,i=n-j;i<n;++i) y[p++]=i;
		for (i=0;i<n;++i) if (sa[i]>=j) y[p++]=sa[i]-j;
		for (i=0;i<n;++i) wv[i]=x[y[i]];
		for (i=0;i<m;++i) Ws[i]=0;
		for (i=0;i<n;++i) Ws[wv[i]]++;
		for (i=0;i<m;++i) Ws[i]+=Ws[i-1];
		for (i=n-1;i>=0;--i) sa[--Ws[wv[i]]]=y[i];
		for (t=x,x=y,y=t,p=1,x[sa[0]]=0,i=1;i<n;i++)
			x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;
	}
}

void calcheight(int *r,int *sa,int n){
	int i,j,k=0;
	for (i=1;i<=n;++i) rank[sa[i]]=i;
	for (i=0;i<n;height[rank[i++]]=k)
	for (k?k--:0,j=sa[rank[i]-1];r[i+k]==r[j+k];k++);
}

bool check(int *sa,int n,int x){
	int i,mx=sa[1],mi=sa[1];
	for (i=2;i<=n;++i){
		if (height[i]<x) mx=mi=sa[i];
		else{
			mx=max(mx,sa[i]);
			mi=min(mi,sa[i]);
			if (mx-mi>x) return 1;
		}
	}return 0;
}

int main(){
	freopen("theme.in","r",stdin);
	freopen("theme.out","w",stdout);
	scanf("%d",&n);
	int fir=read(); n--;
	for (int i=0;i<n;++i){
		int sec=read();
		a[i]=sec-fir+200;
		fir=sec;
	}
	a[n]=0;
	da(a,sa,n+1,500);
	calcheight(a,sa,n);
	int L=1,R,ans=-1;
	if (n&1) R=(n+1)/2;
	else R=n/2;
	while(L<R){
		int mid=(L+R)>>1;
		if (check(sa,n,mid)){
			L=mid+1;
			ans=mid;
		}else R=mid;
	}
	if (ans>=4) printf("%d\n",ans+1);
	else printf("0\n");
}