Java中怎么實現一個雙數組Trie樹

本篇文章給大家分享的是有關Java中怎么實現一個雙數組Trie樹，小編覺得挺實用的，因此分享給大家學習，希望大家閱讀完這篇文章后可以有所收獲，話不多說，跟著小編一起來看看吧。

1.對于插入字符串，如果有一個字符串是另一個字符串的子串的話，我是將結束符也作為一條邊，產生一個新的結點，這個結點新節點的Base我置為0

所以一個字符串結束也有2中情況：一個是Base值為負，存儲剩余字符(可能只有一個結束符)到Tail數組；另一個是Base為0。

所以在查詢的時候要考慮一下這兩種情況

2.對于***種沖突（論文中的Case 3），可能要將Tail中的字符串取出一部分，作為邊放到索引中。論文是使用將尾串左移的方式，我的方式直接修改Base值，而不是移動尾串。

下面是java實現的代碼，可以處理相同字符串插入，子串的插入等情況

/*   * Name:   Double Array Trie   * Author: Yaguang Ding   * Mail: dingyaguang117@gmail.com   * Blog: blog.csdn.net/dingyaguang117   * Date:   2012/5/21   * Note: a word ends may be either of these two case:   * 1. Base[cur_p] == pos  ( pos<0 and Tail[-pos] == 'END_CHAR' )   * 2. Check[Base[cur_p] + Code('END_CHAR')] ==  cur_p   */   import java.util.ArrayList;  import java.util.HashMap;  import java.util.Map;  import java.util.Arrays;    public class DoubleArrayTrie {      final char END_CHAR = '\0';      final int DEFAULT_LEN = 1024;      int Base[]  = new int [DEFAULT_LEN];      int Check[] = new int [DEFAULT_LEN];      char Tail[] = new char [DEFAULT_LEN];      int Pos = 1;      Map<Character ,Integer> CharMap = new HashMap<Character,Integer>();      ArrayList<Character> CharList = new ArrayList<Character>();            public DoubleArrayTrie()      {          Base[1] = 1;                    CharMap.put(END_CHAR,1);          CharList.add(END_CHAR);          CharList.add(END_CHAR);          for(int i=0;i<26;++i)          {              CharMap.put((char)('a'+i),CharMap.size()+1);              CharList.add((char)('a'+i));          }                }      private void Extend_Array()      {          Base = Arrays.copyOf(Base, Base.length*2);          Check = Arrays.copyOf(Check, Check.length*2);      }            private void Extend_Tail()      {          Tail = Arrays.copyOf(Tail, Tail.length*2);      }            private int GetCharCode(char c)      {          if (!CharMap.containsKey(c))          {              CharMap.put(c,CharMap.size()+1);              CharList.add(c);          }          return CharMap.get(c);      }      private int CopyToTailArray(String s,int p)      {          int _Pos = Pos;          while(s.length()-p+1 > Tail.length-Pos)          {              Extend_Tail();          }          for(int i=p; i<s.length();++i)          {              Tail[_Pos] = s.charAt(i);              _Pos++;          }          return _Pos;      }            private int x_check(Integer []set)      {          for(int i=1; ; ++i)          {              boolean flag = true;              for(int j=0;j<set.length;++j)              {                  int cur_p = i+set[j];                  if(cur_p>= Base.length) Extend_Array();                  if(Base[cur_p]!= 0 || Check[cur_p]!= 0)                  {                      flag = false;                      break;                  }              }              if (flag) return i;          }      }            private ArrayList<Integer> GetChildList(int p)      {          ArrayList<Integer> ret = new ArrayList<Integer>();          for(int i=1; i<=CharMap.size();++i)          {              if(Base[p]+i >= Check.length) break;              if(Check[Base[p]+i] == p)              {                  ret.add(i);              }          }          return ret;      }            private boolean TailContainString(int start,String s2)      {          for(int i=0;i<s2.length();++i)          {              if(s2.charAt(i) != Tail[i+start]) return false;          }                    return true;      }      private boolean TailMatchString(int start,String s2)      {          s2 += END_CHAR;          for(int i=0;i<s2.length();++i)          {              if(s2.charAt(i) != Tail[i+start]) return false;          }          return true;      }                  public void Insert(String s) throws Exception      {          s += END_CHAR;                    int pre_p = 1;          int cur_p;          for(int i=0; i<s.length(); ++i)          {              //獲取狀態位置              cur_p = Base[pre_p]+GetCharCode(s.charAt(i));              //如果長度超過現有，拓展數組              if (cur_p >= Base.length) Extend_Array();                            //空閑狀態              if(Base[cur_p] == 0 && Check[cur_p] == 0)              {                  Base[cur_p] = -Pos;                  Check[cur_p] = pre_p;                  Pos = CopyToTailArray(s,i+1);                  break;              }else             //已存在狀態              if(Base[cur_p] > 0 && Check[cur_p] == pre_p)              {                  pre_p = cur_p;                  continue;              }else             //沖突 1：遇到 Base[cur_p]小于0的，即遇到一個被壓縮存到Tail中的字符串              if(Base[cur_p] < 0 && Check[cur_p] == pre_p)              {                  int head = -Base[cur_p];                                    if(s.charAt(i+1)== END_CHAR && Tail[head]==END_CHAR)    //插入重復字符串                  {                      break;                  }                                    //公共字母的情況，因為上一個判斷已經排除了結束符，所以一定是2個都不是結束符                  if (Tail[head] == s.charAt(i+1))                  {                      int avail_base = x_check(new Integer[]{GetCharCode(s.charAt(i+1))});                      Base[cur_p] = avail_base;                                            Check[avail_base+GetCharCode(s.charAt(i+1))] = cur_p;                      Base[avail_base+GetCharCode(s.charAt(i+1))] = -(head+1);                      pre_p = cur_p;                      continue;                  }                  else                 {                      //2個字母不相同的情況，可能有一個為結束符                      int avail_base ;                      avail_base = x_check(new Integer[]{GetCharCode(s.charAt(i+1)),GetCharCode(Tail[head])});                                            Base[cur_p] = avail_base;                                            Check[avail_base+GetCharCode(Tail[head])] = cur_p;                      Check[avail_base+GetCharCode(s.charAt(i+1))] = cur_p;                                            //Tail 為END_FLAG 的情況                      if(Tail[head] == END_CHAR)                          Base[avail_base+GetCharCode(Tail[head])] = 0;                      else                         Base[avail_base+GetCharCode(Tail[head])] = -(head+1);                      if(s.charAt(i+1) == END_CHAR)                           Base[avail_base+GetCharCode(s.charAt(i+1))] = 0;                      else                         Base[avail_base+GetCharCode(s.charAt(i+1))] = -Pos;                                            Pos = CopyToTailArray(s,i+2);                      break;                  }              }else             //沖突2：當前結點已經被占用，需要調整pre的base              if(Check[cur_p] != pre_p)              {                  ArrayList<Integer> list1 = GetChildList(pre_p);                  int toBeAdjust;                  ArrayList<Integer> list = null;                  if(true)                  {                      toBeAdjust = pre_p;                      list = list1;                  }                                    int origin_base = Base[toBeAdjust];                  list.add(GetCharCode(s.charAt(i)));                  int avail_base = x_check((Integer[])list.toArray(new Integer[list.size()]));                  list.remove(list.size()-1);                                    Base[toBeAdjust] = avail_base;                  for(int j=0; j<list.size(); ++j)                  {                      //BUG                       int tmp1 = origin_base + list.get(j);                      int tmp2 = avail_base + list.get(j);                                            Base[tmp2] = Base[tmp1];                      Check[tmp2] = Check[tmp1];                                            //有后續                      if(Base[tmp1] > 0)                      {                          ArrayList<Integer> subsequence = GetChildList(tmp1);                          for(int k=0; k<subsequence.size(); ++k)                          {                              Check[Base[tmp1]+subsequence.get(k)] = tmp2;                          }                      }                                            Base[tmp1] = 0;                      Check[tmp1] = 0;                  }                                    //更新新的cur_p                  cur_p = Base[pre_p]+GetCharCode(s.charAt(i));                                    if(s.charAt(i) == END_CHAR)                      Base[cur_p] = 0;                  else                     Base[cur_p] = -Pos;                  Check[cur_p] = pre_p;                  Pos = CopyToTailArray(s,i+1);                  break;              }          }      }            public boolean Exists(String word)      {          int pre_p = 1;          int cur_p = 0;                    for(int i=0;i<word.length();++i)          {              cur_p = Base[pre_p]+GetCharCode(word.charAt(i));              if(Check[cur_p] != pre_p) return false;              if(Base[cur_p] < 0)              {                  if(TailMatchString(-Base[cur_p],word.substring(i+1)))                      return true;                  return false;              }              pre_p = cur_p;          }          if(Check[Base[cur_p]+GetCharCode(END_CHAR)] == cur_p)              return true;          return false;      }            //內部函數，返回匹配單詞的最靠后的Base index，      class FindStruct      {          int p;          String prefix="";      }      private FindStruct Find(String word)      {          int pre_p = 1;          int cur_p = 0;          FindStruct fs = new FindStruct();          for(int i=0;i<word.length();++i)          {              // BUG              fs.prefix += word.charAt(i);              cur_p = Base[pre_p]+GetCharCode(word.charAt(i));              if(Check[cur_p] != pre_p)              {                  fs.p = -1;                  return fs;              }              if(Base[cur_p] < 0)              {                  if(TailContainString(-Base[cur_p],word.substring(i+1)))                  {                      fs.p = cur_p;                      return fs;                  }                  fs.p = -1;                  return fs;              }              pre_p = cur_p;          }          fs.p =  cur_p;          return fs;      }            public ArrayList<String> GetAllChildWord(int index)      {          ArrayList<String> result = new ArrayList<String>();          if(Base[index] == 0)          {              result.add("");              return result;          }          if(Base[index] < 0)          {              String r="";              for(int i=-Base[index];Tail[i]!=END_CHAR;++i)              {                  r+= Tail[i];              }              result.add(r);              return result;          }          for(int i=1;i<=CharMap.size();++i)          {              if(Check[Base[index]+i] == index)              {                  for(String s:GetAllChildWord(Base[index]+i))                  {                      result.add(CharList.get(i)+s);                  }                  //result.addAll(GetAllChildWord(Base[index]+i));              }          }          return result;      }            public ArrayList<String> FindAllWords(String word)      {          ArrayList<String> result = new ArrayList<String>();          String prefix = "";          FindStruct fs = Find(word);          int p = fs.p;          if (p == -1) return result;          if(Base[p]<0)          {              String r="";              for(int i=-Base[p];Tail[i]!=END_CHAR;++i)              {                  r+= Tail[i];              }              result.add(fs.prefix+r);              return result;          }                    if(Base[p] > 0)          {              ArrayList<String> r =  GetAllChildWord(p);              for(int i=0;i<r.size();++i)              {                  r.set(i, fs.prefix+r.get(i));              }              return r;          }                    return result;      }        }

測  試

import java.io.BufferedReader;  import java.io.FileInputStream;  import java.io.IOException;  import java.io.InputStream;  import java.io.InputStreamReader;  import java.util.ArrayList;  import java.util.Scanner;   import javax.xml.crypto.Data;    public class Main {       public static void main(String[] args) throws Exception {          ArrayList<String> words = new ArrayList<String>();          BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream("E:/兔子的試驗學習中心[課內]/ACM大賽/ACM第四屆校賽/E命令提示/words3.dic")));          String s;          int num = 0;          while((s=reader.readLine()) != null)          {              words.add(s);              num ++;          }          DoubleArrayTrie dat = new DoubleArrayTrie();                    for(String word: words)          {              dat.Insert(word);          }                    System.out.println(dat.Base.length);          System.out.println(dat.Tail.length);                    Scanner sc = new Scanner(System.in);          while(sc.hasNext())          {              String word = sc.next();              System.out.println(dat.Exists(word));              System.out.println(dat.FindAllWords(word));          }                }   }

下面是測試結果，構造6W英文單詞的DAT，大概需要20秒

我增長數組的時候是每次長度增加到2倍，初始1024

Base和Check數組的長度為131072

Tail的長度為262144

以上就是Java中怎么實現一個雙數組Trie樹，小編相信有部分知識點可能是我們日常工作會見到或用到的。希望你能通過這篇文章學到更多知識。更多詳情敬請關注億速云行業資訊頻道。