hdu1238 Substrings 扩展KMP

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.

找出最长的一个子串，所有串中都出现过它或它的逆序

扩展KMP水题

 #include<stdio.h>
 #include<string.h>
 #include<iostream>
 #include<string>
 #include<algorithm>
 using namespace std;

 const int maxn=;
 int nxt[][maxn],ext[][maxn];
 char s[][maxn];
 int len[],ans[maxn];

 void EKMP(char s[],char t[],int lens,int lent,int c){
     int i,j,p,l,k;
     nxt[c][]=lent;j=;
     while(j+<lent&&t[j]==t[j+])j++;
     nxt[c][]=j;
     k=;
     for(i=;i<lent;i++){
         p=nxt[c][k]+k-;
         l=nxt[c][i-k];
         if(i+l<p+)nxt[c][i]=l;
         else{
             j=max(,p-i+);
             while(i+j<lent&&t[i+j]==t[j])j++;
             nxt[c][i]=j;
             k=i;
         }
     }

     j=;
     while(j<lens&&j<lent&&s[j]==t[j])j++;
     ext[c][]=j;k=;
     for(i=;i<lens;i++){
         p=ext[c][k]+k-;
         l=nxt[c][i-k];
         if(l+i<p+)ext[c][i]=l;
         else{
             j=max(,p-i+);
             while(i+j<lens&&j<lent&&s[i+j]==t[j])j++;
             ext[c][i]=j;
             k=i;
         }
     }
 }

 int main(){
     int T;
     scanf("%d",&T);
     while(T--){
         memset(ans,0x3f,sizeof(ans));
         int n;
         scanf("%d",&n);
         for(int i=;i<=n;++i)scanf("%s",s[i]);
         for(int i=;i<=n;++i)len[i]=strlen(s[i]);
         s[][len[]]='#';
         for(int i=;i<=len[];++i)s[][len[]+i]=s[][len[]-i];
         s[][len[]+len[]+]=;
         len[]=strlen(s[]);
         int maxx=;
         for(int i=;i<len[];++i){
             for(int j=;j<=n;++j){
                 int cnt=;
                 EKMP(s[j],s[]+i,len[j],len[]-i,j);
                 for(int k=;k<len[j];++k){
                     if(ext[j][k]>cnt)cnt=ext[j][k];
                 }
                 if(cnt<ans[i])ans[i]=cnt;
             }
             if(ans[i]>maxx)maxx=ans[i];
         }
         printf("%d\n",maxx);
     }
     return ;
 }