SPOJLCS

Posted 2022-06-01 shxnb666

题面

https://vjudge.net/problem/SPOJ-LCS

题解

#include<cstdio>
#include<iostream>
#include<cstring>
#define ri register int
#define N 100050
using namespace std;
char s1[N],s2[N];
struct SAM
  int ff[N<<1],len[N<<1];
  int ch[N<<1][26];
  int last,tot;
  inline void clear() 
    last=tot=1;
    memset(ch,0,sizeof(ch));
  
  inline void extend(int c) 
    int p,np,q,nq;
    p=last;np=++tot;last=tot;len[np]=len[p]+1;
    while(p && !ch[p][c]) ch[p][c]=np,p=ff[p];
    if (!p) ff[np]=1;
    else 
      q=ch[p][c];
      if (len[q]==len[p]+1) 
        ff[np]=q;
      
      else 
        nq=++tot;
        len[nq]=len[p]+1;
        for (ri i=0;i<26;i++) ch[nq][i]=ch[q][i]; ff[nq]=ff[q];
        ff[np]=ff[q]=nq;
        while (p && ch[p][c]==q) ch[p][c]=nq,p=ff[p];
      
    
  

  inline int match() 
    int ret=0;
    int cnt=0,now=1;
    for (ri i=1,l=strlen(s2+1);i<=l;i++) 
      if (ch[now][s2[i]-‘a‘]) 
        cnt++;
        now=ch[now][s2[i]-‘a‘];
        ret=max(ret,cnt);
      
      else 
        while (now && !ch[now][s2[i]-‘a‘]) now=ff[now];
        if (!now) 
          cnt=0;
          now=1;
          continue;
        
        else 
          cnt=len[now]+1;
          ret=max(ret,cnt);
          now=ch[now][s2[i]-‘a‘];
        
      
    
    return ret;
  
 sam;

int main()
  scanf("%s%s",s1+1,s2+1);
  sam.clear();
  for (ri i=1,l=strlen(s1+1);i<=l;i++) sam.extend(s1[i]-‘a‘);
  printf("%d\n",sam.match());
  return 0;