POJ3581:Sequence(后缀数组)

Description

Given a sequence, {A₁, A₂, ..., A_n} which is guaranteed A₁> A₂, ..., A_n, you are to cut it into three sub-sequences and reverse them
separately to form a new one which is the smallest possible sequence in alphabet order.

The alphabet order is defined as follows: for two sequence {A₁, A₂, ..., A_n} and {B₁, B₂, ..., B_n}, we say {A₁, A₂,
..., A_n} is smaller than {B₁, B₂, ..., B_n} if and only if there exists such i ( 1 ≤ i ≤ n) so that we have A_i < B_{i and}A_j = B_j for
each j < i.

Input

The first line contains n. (n ≤ 200000)

The following n lines contain the sequence.

Output

output n lines which is the smallest possible sequence obtained.

Sample Input

Sample Output

Hint

{10, 1, 2, 3, 4} -> {10, 1 | 2 | 3, 4} -> {1, 10, 2, 4, 3}

题意：把数组分成3分，每一份都翻转。要求输出字典序最小的结果

思路：參照http://blog.163.com/just_gogo/blog/static/1914390652011823103842787/

第二次求之所以要复制一次我们能够这样理解

首先320505。单纯这个的话，后缀按字典序排，第一是05，第二是0505

可是复制了之后，是第一是0505320505，第二是05320505

可见复制一遍还是有必要的

#include <iostream>

#include <stdio.h>

#include <string.h>

#include <stack>

#include <queue>

#include <map>

#include <set>

#include <vector>

#include <math.h>

#include <bitset>

#include <algorithm>

#include <climits>

using namespace std;

#define LS 2*i

#define RS 2*i+1

#define UP(i,x,y) for(i=x;i<=y;i++)

#define DOWN(i,x,y) for(i=x;i>=y;i--)

#define MEM(a,x) memset(a,x,sizeof(a))

#define W(a) while(a)

#define gcd(a,b) __gcd(a,b)

#define LL long long

#define N 2000005

#define MOD 1000000007

#define INF 0x3f3f3f3f

#define EXP 1e-8

int wa[N],wb[N],wsf[N],wv[N],sa[N];

int rank[N],height[N],s[N];

//sa:字典序中排第i位的起始位置在str中第sa[i]

//rank:就是str第i个位置的后缀是在字典序排第几

//height：字典序排i和i-1的后缀的最长公共前缀

int cmp(int *r,int a,int b,int k)

{

    return r[a]==r[b]&&r[a+k]==r[b+k];

}

void getsa(int *r,int *sa,int n,int m)//n要包括末尾加入的0

{

    int i,j,p,*x=wa,*y=wb,*t;

    for(i=0; i<m; i++)  wsf[i]=0;

    for(i=0; i<n; i++)  wsf[x[i]=r[i]]++;

    for(i=1; i<m; i++)  wsf[i]+=wsf[i-1];

    for(i=n-1; i>=0; i--)  sa[--wsf[x[i]]]=i;

    p=1;

    j=1;

    for(; p<n; j*=2,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++)  wsf[i]=0;

        for(i=0; i<n; i++)  wsf[wv[i]]++;

        for(i=1; i<m; i++)  wsf[i]+=wsf[i-1];

        for(i=n-1; i>=0; i--)  sa[--wsf[wv[i]]]=y[i];

        t=x;

        x=y;

        y=t;

        x[sa[0]]=0;

        for(p=1,i=1; i<n; i++)

            x[sa[i]]=cmp(y,sa[i-1],sa[i],j)? p-1:p++;

    }

}

struct node

{

    int id,num;

} a[N];

int cmp1(node a,node b)

{

    if(a.num!=b.num)

        return a.num<b.num;

    return a.id<b.id;

}

int main()

{

    int n,i,j,k,maxn;

    scanf("%d",&n);

    for(i = n-1; i>=0; i--)

    {

        scanf("%d",&a[i].num);

        a[i].id = i;

    }

    sort(a,a+n,cmp1);

    for(i = 0; i<n; i++)

    {

        if(i && a[i].num == a[i-1].num)

        {

            s[a[i].id] = s[a[i-1].id];

            continue;

        }

        s[a[i].id] = i+1;

    }

    s[n] = 0;

    getsa(s,sa,n+1,n+10);

    for(i = 1; i<=n&&sa[i]<=1; i++);

    int tem = sa[i];

    for(i = tem; i<n; i++)

        printf("%d\n",a[s[i]-1].num);

    for(i = 0; i<tem; i++)

        s[i+tem] = s[i];

    tem*=2;

    s[tem] = 0;

    getsa(s,sa,tem+1,n+10);

    int p;

    for(i = 1; i<tem&&(!sa[i]||sa[i]>=tem/2); i++) ;

    p = sa[i];

    for(i = p; i<tem/2; i++)

        printf("%d\n",a[s[i]-1].num);

    for(i = 0; i<p; i++)

        printf("%d\n",a[s[i]-1].num);

    return 0;

}

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POJ3581:Sequence(后缀数组)

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