M - Substrings

You are given a number of case-sensitive strings of alphabetic characters, find the largest string X, such that either X, or its inverse can be found as a substring of any of the given strings. 

InputThe first line of the input file contains a single integer t (1 <= t <= 10), the number of test cases, followed by the input data for each test case. The first line of each test case contains a single integer n (1 <= n <= 100), the number of given strings, followed by n lines, each representing one string of minimum length 1 and maximum length 100. There is no extra white space before and after a string. 
OutputThere should be one line per test case containing the length of the largest string found. 
Sample Input

2
3
ABCD
BCDFF
BRCD
2
rose
orchid

Sample Output

2
2

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<vector>
#include <sstream>
#include<string>
#include<cstring>
#include<list>
using namespace std;
#define MAXN 102
#define INF 0x3f3f3f3f
#define M 10007
typedef long long LL;
/*
枚举第一个串的所有子串 找到就停止
*/
char s[MAXN][MAXN];
int Next[MAXN];
void kmp_pre(char t[])
{
    int m = strlen(t);
    int j,k;
    j = 0;k = Next[0] = -1;
    while(j<m)
    {
        if(k==-1||t[j]==t[k])
            Next[++j] = ++k;
        else
            k = Next[k];
    }
}
bool KMP(char t[],char s[])
{
    kmp_pre(t);
    int n = strlen(s),m=strlen(t);
    int i,j;
    j = 0;
    for(i=0;i<n;i++)
    {
        while(j>0&&s[i]!=t[j])
            j = Next[j];
        if(s[i]==t[j])
            j++;
        if(j>=m)
            return true;
    }
    return false;
}
int main()
{
    int T,n;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n);
        for(int i=0;i<n;i++)
            scanf("%s",s[i]);
        int len = strlen(s[0]);
        bool f = false;
        for(int l=len;l>0;l--)
        {
            for(int i=0;i+l<=len;i++)
            {
                char t1[MAXN] = {0},t2[MAXN] = {0};
                strncpy(t1,s[0]+i,l);
                for(int j=0;j<l;j++)
                    t2[j] = t1[l-1-j];
                int j;
                //cout<<t1<<endl<<t2<<endl;
                for(j=1;j<n;j++)
                {
                    if(KMP(t1,s[j])
                        ||KMP(t2,s[j]))
                        continue;
                    else
                        break;
                }
                if(j==n)
                {
                    f = true;
                    printf("%d\n",l);
                    i = INF;
                    l = -1;
                }
            }
        }
        if(!f)
            printf("0\n");
    }
}