SPOJ PHRASES 每个字符串至少出现两次且不重叠的最长子串

 

Description

You are the King of Byteland. Your agents have just intercepted a batch of encrypted enemy messages concerning the date of the planned attack on your island. You immedietaly send for the Bytelandian Cryptographer, but he is currently busy eating popcorn and claims that he may only decrypt the most important part of the text (since the rest would be a waste of his time). You decide to select the fragment of the text which the enemy has strongly emphasised, evidently regarding it as the most important. So, you are looking for a fragment of text which appears in all the messages disjointly at least twice. Since you are not overfond of the cryptographer, try to make this fragment as long as possible.

Input

The first line of input contains a single positive integer t<=10, the number of test cases. t test cases follow. Each test case begins with integer n (n<=10), the number of messages. The next n lines contain the messages, consisting only of between 2 and 10000 characters 'a'-'z', possibly with some additional trailing white space which should be ignored.

Output

For each test case output the length of longest string which appears disjointly at least twice in all of the messages.

Example

Input:
1
4
abbabba
dabddkababa
bacaba
baba

Output:
2

 

/*
SPOJ PHRASES 每个字符串至少出现两次且不重叠的最长子串

因为是求的最长子串，所以考虑二分长度len
然后我们需要对其进行判断，对于每一个连续大于等于len的height[](分组讨论)
记录各个串中的情况，因为要判断不是重叠的，所以对于每个串，我们记录
它满足height>=len的最大最小位置
如果所有串的max-min >= len 则说明存在长度为len的子串在
每个串都有出现两次且不重叠

感觉思路没什么问题，主要是最开始代码写得不够简洁，而且WR

hhh-2016-03-21 23:01:01
*/
#include <algorithm>
#include <cmath>
#include <queue>
#include <iostream>
#include <cstring>
#include <map>
#include <cstdio>
#include <vector>
#include <functional>
#define lson (i<<1)
#define rson ((i<<1)|1)
using namespace std;
typedef long long ll;
const int maxn = 101000;

int t1[maxn],t2[maxn],c[maxn];
bool cmp(int *r,int a,int b,int l)
{
    return r[a]==r[b] &&r[l+a] == r[l+b];
}

void get_sa(int str[],int sa[],int Rank[],int height[],int n,int m)
{
    n++;
    int p,*x=t1,*y=t2;
    for(int i = 0; i < m; i++) c[i] = 0;
    for(int i = 0; i < n; i++) c[x[i] = str[i]]++;
    for(int i = 1; i < m; i++) c[i] += c[i-1];
    for(int i = n-1; i>=0; i--) sa[--c[x[i]]] = i;
    for(int j = 1; j <= n; j <<= 1)
    {
        p = 0;
        for(int i = n-j; i < n; i++) y[p++] = i;
        for(int i = 0; i < n; i++) if(sa[i] >= j) y[p++] = sa[i]-j;
        for(int i = 0; i < m; i++) c[i] = 0;
        for(int i = 0; i < n; i++) c[x[y[i]]]++ ;
        for(int i = 1; i < m; i++) c[i] += c[i-1];
        for(int i = n-1; i >= 0; i--)  sa[--c[x[y[i]]]] = y[i];

        swap(x,y);
        p = 1;
        x[sa[0]] = 0;
        for(int i = 1; i < n; i++)
            x[sa[i]] = cmp(y,sa[i-1],sa[i],j)? p-1:p++;
        if(p >= n) break;
        m = p;
    }
    int k = 0;
    n--;
    for(int i = 0; i <= n; i++)
        Rank[sa[i]] = i;
    for(int i = 0; i < n; i++)
    {
        if(k) k--;
        int j = sa[Rank[i]-1];
        while(str[i+k] == str[j+k]) k++;
        height[Rank[i]] = k;
    }
}

int Rank[maxn];
int sa[maxn];
int str[maxn],height[maxn];
char s[maxn];
int id[maxn];
struct node
{
    int Min;
    int Max;
    int flag;
} anspos[15];


void ini()
{
    for(int i = 0; i <= 12; i++)
        anspos[i].Min = 0x3f3f3f3f,anspos[i].Max = -1;
}

bool can(int len,int n,int num)
{
    int l = 2,r = 2;
    ini();
    for(int i = 2; i <= n; i++)
    {
        if(height[i] >= len)
        {
            int id1=id[sa[i-1]];
            int id2=id[sa[i]];

            anspos[id1].Max=max(anspos[id1].Max,sa[i-1]);
            anspos[id1].Min=min(anspos[id1].Min,sa[i-1]);

            anspos[id2].Max=max(anspos[id2].Max,sa[i]);
            anspos[id2].Min=min(anspos[id2].Min,sa[i]);
            int t;
            for(t = 0; t < num; t++)
                if(anspos[t].Max - anspos[t].Min < len)
                    break;
            if(t == num)
                return 1;
        }
        else
        {
            for(int j = 0; j <= 10; j++)
                anspos[j].Min = 0x3f3f3f3f,anspos[j].Max = -1;
        }
    }
    for(int i = 0; i < num; i++)
        if(!anspos[i].flag)
            return 0;
    return 1;
}

int main()
{
    int k,n,t;
    scanf("%d",&t);
    while(t--)
    {
        ini();
        int tot = 0,len = 0x3f3f3f3f;
        scanf("%d",&n);
        for(int i = 0; i < n; i++)
        {
            scanf("%s",s);
            for(int j = 0; s[j]!='\0'; j++)
            {
                id[tot] = i;
                str[tot++] = s[j]-'a'+10;
            }
            id[tot] = i;
            str[tot++] = i;
            len = min(len,(int)strlen(s));
        }
        str[tot] = 0;
        get_sa(str,sa,Rank,height,tot,100);
        int l = 0,r = len;
        int ans = 0;
        while(l <= r)
        {
            int mid = (l+r)>>1;
            if(can(mid,tot,n))
            {
                ans = mid;
                l = mid+1;
            }
            else
                r = mid-1;
        }
        printf("%d\n",ans);
    }
    return 0;
}