后缀自动机

BZOJ3998

#include <cstdio>
#include <cstring>
using namespace std;

  int last,dis[1000011],fa[1000011],a[1000011][26],cnt,sum[1000011];
  int val[1000011],n,dl[1000011],T,k;
  char st[1000011];

  void ins(int num){
      int p=last,np=last=++cnt;
      dis[np]=dis[p]+1;val[np]=1;
      while (!a[p][num]&&p) a[p][num]=np,p=fa[p];
      if (!p) fa[np]=1;else{
        int q=a[p][num];
        if (dis[p]+1==dis[q]) fa[np]=q;else{
          int nq=++cnt;dis[nq]=dis[p]+1;
        memcpy(a[nq],a[q],sizeof(a[q]));
        fa[nq]=fa[q];
        fa[q]=fa[np]=nq;
        while (a[p][num]==q) a[p][num]=nq,p=fa[p];
      }
    }
  }

  void init(){
       for (int i=1;i<=cnt;i++) sum[dis[i]]++;
      for (int i=1;i<=n;i++) sum[i+1]+=sum[i];
      for (int i=cnt;i>0;i--) dl[sum[dis[i]]--]=i;
      for (int i=1;i<=cnt;i++) sum[i]=0;
      
      for (int i=cnt;i>0;i--){
        int t=dl[i];
      if (T==1) val[fa[t]]+=val[t];else val[t]=1;
    }
    val[1]=0;
    for (int i=cnt;i>0;i--){
      int t=dl[i];sum[t]=val[t];
      for (int j=0;j<26;j++)
        sum[t]+=sum[a[t][j]];
    }
  }

  void dfs(int po,int num){
      if (num<=val[po]) return;
      num-=val[po];
      for (int i=0;i<26;i++)
        if (a[po][i]){
          if (num<=sum[a[po][i]]){
            putchar('a'+i);
          dfs(a[po][i],num);
          return;    
        }
        num-=sum[a[po][i]];
      }
  }

  int main(){
      scanf("%s",&st);
      scanf("%d%d",&T,&k);
      
      last=cnt=1;dis[1]=1;n=strlen(st);
      for (int i=0;i<n;i++)
        ins(st[i]-'a');
        
      init();
      
      if (k>sum[1]) printf("-1\n");else dfs(1,k);
  }

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BZOJ2806

#include <cstdio>
#include <iostream>
#include <cstring>
using namespace std;

  int last,cnt,dis[3000001],a[3000001][3],fa[3000001],mat[3000001];
  int dp[3000001];
  char st[3000001];

  void insert(int num){
      int p=last,np=last=++cnt;
      dis[np]=dis[p]+1;
      while (!a[p][num]&&p) a[p][num]=np,p=fa[p];
      if (!p) fa[np]=1;else{
        int q=a[p][num];
        if (dis[p]+1==dis[q]) fa[np]=q;else{
          int nq=++cnt;dis[nq]=dis[p]+1;
        memcpy(a[nq],a[q],sizeof(a[q]));
        fa[nq]=fa[q];
        fa[q]=fa[np]=nq;
        while (a[p][num]==q) a[p][num]=nq,p=fa[p];
      }
    }
  }

  void pre(int len){
      int po=1,cnt=0;
      for (int i=1;i<=len;i++){
        int num=st[i]-'0';
        if (a[po][num]) cnt++,po=a[po][num];else{
          while (po&&!a[po][num]) po=fa[po];    
          if (po) cnt=dis[po]+1,po=a[po][num];else 
                  cnt=0,po=1;
      }
      mat[i]=cnt;
    }
  }//以任意位置结尾的最长匹配长度
  
  struct dddl{
      int top,but,num[1000001],pos[1000001];
      
      void push(int po,int nu){
        while (top>=but&&nu>=num[top]) top--;
        top++;num[top]=nu;pos[top]=po;
    }
    
    void pop(int po){
      while (top>=but&&pos[but]<po) but++;
    }
    
    int get(){
      return(num[but]);
    }
  }dl;
  
  int check(int mid,int len){
      for (int i=0;i<=len;i++) dp[i]=0;
      dl.top=0;dl.but=1;
      for (int i=1;i<=len;i++){
        dp[i]=dp[i-1];
        if (i>=mid) dl.push(i-mid,dp[i-mid]-(i-mid));
      dl.pop(i-mat[i]);
      if (dl.top>=dl.but) dp[i]=max(dl.get()+i,dp[i]);    
    }
    if (dp[len]*10>=len*9) return(1);else return(0);
  }

  int main(){
      int n,m;
      scanf("%d%d",&n,&m);
      cnt=1;last=1;
      for (int i=1;i<=m;i++){
        scanf("%s",&st);
      int t=strlen(st);
      for (int j=0;j<t;j++)
        insert(st[j]-'0');
      insert(2);    
    }
    
    while (n--){
      scanf("%s",st+1);    
      int len=strlen(st+1);
      pre(len);
      
      int l=1,r=len;
      while (l<r){
          int mid=(l+r+1)>>1;
          if (check(mid,len)) l=mid;else r=mid-1;
      }
      if (check(l,len)) printf("%d\n",l);else printf("0\n");
    }
  }

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BZOJ4032

#include <cstdio>
#include <cstring>
using namespace std;

  int vis[4001][4001],dl[16000001][3],head,tail;
  char A[4001],B[4001];

  struct automaton{
      int last,cnt,dis[4001],fa[4001],a[4001][26];
      
      void insert(int num){
        int p=last,np=last=++cnt;
      dis[np]=dis[p]+1;
      while (p&&!a[p][num]) a[p][num]=np,p=fa[p];
      if (!p) fa[np]=1;else{
          int q=a[p][num];
          if (dis[q]==dis[p]+1) fa[np]=q;else{
            int nq=++cnt;dis[nq]=dis[p]+1;
          memcpy(a[nq],a[q],sizeof(a[q]));
          fa[nq]=fa[q];
          fa[q]=fa[np]=nq;
          while (a[p][num]==q) a[p][num]=nq,p=fa[p];
        }
      }    
    }
      
      void build1(char st[]){
        int n=strlen(st+1);
      cnt=1;last=1;
      for (int i=1;i<=n;i++)    
        insert(st[i]-'a');
    }
    
    void build2(char st[]){
      int n=strlen(st+1);cnt=n+1;
      for (int i=n;i>=1;i--){
          memcpy(a[i],a[i+1],sizeof(a[i+1]));
          a[i][st[i]-'a']=i+1;
      }
    }
  }a1,a2,b1,b2;

  void bfs(automaton &a,automaton &b){
      for (int i=1;i<=a.cnt;i++) for (int j=1;j<=b.cnt;j++) vis[i][j]=0;
      vis[1][1]=1;
      dl[head=tail=1][0]=1;dl[1][1]=1;dl[1][2]=0;
      while (head<=tail){
        for (int i=0;i<26;i++){
            int t1=a.a[dl[head][0]][i],t2=b.a[dl[head][1]][i];
            if (t1&&!t2) {printf("%d\n",dl[head][2]+1);return;}
            if (t1&&t2&&!vis[t1][t2]){
              tail++;
              dl[tail][0]=t1;dl[tail][1]=t2;dl[tail][2]=dl[head][2]+1;
          vis[t1][t2]=1;    
        }
      }
      head++;    
    }
  }

  int main(){
      scanf("%s",A+1);scanf("%s",B+1);
      a1.build1(A);a2.build2(A);
      b1.build1(B);b2.build2(B);
      
      bfs(a1,b1);
      bfs(a1,b2);
      bfs(a2,b1);
      bfs(a2,b2);
  }