SPOJ lcs2 Longest Common Substring II 后缀自动机
来源:互联网 发布:斯洛文尼亚 旅行 知乎 编辑:程序博客网 时间:2024/05/22 17:23
题意:求n个串的最长公共子串(连续的)
方法:用其中一串构建后缀自动机,其它串来跑,并更新其len(step)即答案。
PS:本来是另一开一个数组来记录时间的,但状态转移时要用到SAM_node的标号,增加了时间复杂度常数,被卡了时间
#include <stdio.h>#include <stdlib.h>#include <vector>#include <algorithm>#include <iostream>#include <math.h>#include <string.h>using namespace std;typedef long long ll;const int Mod=1e9+7;const int N=1e5+5;int n;struct SAM_Node{ SAM_Node *fa,*next[26]; int len; int pos,temp; SAM_Node(){} SAM_Node(int _len){ fa=0;len=_len;temp=0; memset(next,0,sizeof(next)); }};SAM_Node SAM_node[N<<1],*SAM_root,*SAM_last,*b[N<<1];int SAM_size;SAM_Node *newSAM_Node(int len){ SAM_node[SAM_size]=SAM_Node(len); SAM_node[SAM_size].pos=SAM_size; return &SAM_node[SAM_size++];}SAM_Node *newSAM_Node(SAM_Node *p){ SAM_node[SAM_size]=*p; SAM_node[SAM_size].pos=SAM_size; return &SAM_node[SAM_size++];}void SAM_init(){ SAM_size=0; SAM_root=SAM_last=newSAM_Node(0); SAM_node[0].pos=0;}void SAM_add(int x,int len){ SAM_Node *p=SAM_last,*np=newSAM_Node(p->len+1); SAM_last=np; for(;p&&!p->next[x];p=p->fa)p->next[x]=np; if(!p){ np->fa=SAM_root; return; } SAM_Node *q=p->next[x]; if(q->len==p->len+1){ np->fa=q; return; } //puts("3"); SAM_Node *nq=newSAM_Node(q); nq->len=p->len+1; q->fa=nq; np->fa=nq; for(;p&&p->next[x]==q;p=p->fa)p->next[x]=nq;}char a[N];int dp[N<<1];int rank[N<<1],cnt[N<<1];void Sort(){ memset(cnt,0,sizeof(cnt)); for(int i=0;i<SAM_size;i++) cnt[SAM_node[i].len]++; for(int i=1;i<=n;i++) cnt[i]+=cnt[i-1]; for(int i=0;i<SAM_size;i++){ //rank[--cnt[SAM_node[i].len]]=i; b[--cnt[SAM_node[i].len]]=&SAM_node[i]; }}void work(){ int T; SAM_init(); scanf("%s",a+1); n=strlen(a+1); for(int i=1;i<=n;i++) SAM_add(a[i]-'a',i); Sort(); int ret=0;// for(int i=0;i<SAM_size;i++)// cnt[i]=SAM_node[i].len; while(~scanf("%s",a+1)){ n=strlen(a+1); SAM_Node *Cur=SAM_root; int temp=0; for(int i=1;i<=n;i++){ int u=a[i]-'a'; if(Cur->next[u]){ temp++; Cur=Cur->next[u]; } else{ while(true){ Cur=Cur->fa; if(!Cur)break; if(Cur->next[u])break; } if(!Cur){ Cur=SAM_root;temp=0; } else{ temp=Cur->len+1; Cur=Cur->next[u]; } } //u=Cur->pos; //dp[u]=max(dp[u],temp);Cur->temp=max(Cur->temp,temp); } int u,v; for(int i=SAM_size-1;i>0;i--){ //u=rank[i]; //v=SAM_node[u].fa->pos; //dp[v]=max(dp[v],dp[u]); //cnt[u]=min(cnt[u],dp[u]); //dp[u]=0; //u=b[i]->pos;v=b[i]->fa->pos; //dp[v]=max(dp[v],dp[u]); //b[i]->len=min(b[i]->len,dp[u]); //dp[u]=0;b[i]->fa->temp=max(b[i]->fa->temp,b[i]->temp);b[i]->len=min(b[i]->len,b[i]->temp);b[i]->temp=0; } } for(int i=1;i<SAM_size;i++) ret=max(ret,b[i]->len); printf("%d\n",ret);}int main(){ freopen("data_in.txt","r",stdin); //freopen("C_out.txt","w",stdout); work(); return 0;}
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