[C + +] data structures for separating and linking the hash table

　　Hash list, called hash table in English, is also called a hash table, is a data structure based on the key value to determine the storage location in main memory. A hash function (a function of the key value) is adopted to determine where to store the keyword.

The main methods are: 1. Separating link method (Zipper method)

The hash function for the detach link method is position = key% n. That is, the keyword's storage location is the value of the keyword to model the number of table items. If the table item size is 13, for items with a key value of 27, the table key is stored at 1 (27 13 = 1). To reduce conflicts, n tends to take primes. , using a queue (linked list) to join together, the newly placed elements into the team head or the end of the team can be. The picture is described as follows:

　　2. Linear probing method

Linear probing is based on the number of collisions, to avoid collisions from the target position after the collision, that is, position_new = (position + i)% n, where I is the number of collisions, n is the table item size.

3. Square Probing method

Similar to linear probing, except that the hash function is different, its position_new = (position + i2)% n

4. Double hash, re-hash, etc.

　The structure of the data structure of the data structure that separates the link method uses a class named Hashtable to encapsulate the operations and properties of the entire table. Use vector<deque<int>> to represent the entire data structure, that is, the entire table is a single (double-ended)

A vector (array) of queues. The class also contains other functions that are used to access private properties in the class.

The declaration of the class is as follows:

1 classHashTable {2      Public:3HashTable (int= One);4~hashtable () =default;5         intGethashitemsize (Const int)Const;//Get Queue Length6         intGethashtablesize ()Const;//get the size of a table item7         BOOLInsertrecord (int);//Insert a value8         voidRemoveRecord (Const int);//Delete a value9         BOOLIsEmpty ()Const;//determine if the hash table is emptyTen         voidPrint ()Const;//Print Hash Table One  A     Private: -vector<deque<int>> Hashitem;//structure Definition -         intHashtablesize =0;//Number of hash table entries the};

　　

Constructor definition:

　　

1Hashtable::hashtable (intN//constructor Definition2 {3Hashtablesize =N;4 5      for(inti =0; I < n; ++i)6     {7deque<int>Adeque;8Hashitem.push_back (Adeque);//to push a sufficient empty queue into the vector9     }Ten}

The definition of the function that inserted the record:

1 BOOLHashtable::insertrecord (intData//inserts a record of a specified value2 {3     intPosition = data% Hashtablesize;//Mapping Rules4 5     if(Position >= Hashtablesize | | position <0)//Judgment of legality6         return false;7 8     Else9     {Tenhashitem.at (position). Push_front (data);//according to the principle of time locality, inserting into the team head One         return true; A     } -}

Delete a function definition for a record

1 voidHashtable::removerecord (Const intAim//Delete a record of a specified value2 {3     inti =0;4     intj =0;5 6      for(; i < hashtablesize; ++i)//traversing table Entries7     {8 9          for(j =0; J < static_cast<int> (hashitem.at (i). Size ()); ++J)//Traverse QueueTen         { One             if(Hashitem.at (i). at (j) = =aim) Ahashitem.at (i). Erase (hashitem.at (i). Begin () + j);//Deleting Records -         } -     } the  -}

Print function:

1 voidHashTable::p rint ()Const2 {3      for(inti =0; I < gethashtablesize (); ++i)//traversing table Entries4     {5deque<int> temp =hashitem.at (i);6 7          for(Auto &j:temp)//Traverse Queue8cout << J <<' ';9 Tencout <<Endl; One     } A}

For the main function, write a little test statement to test:

1 intMain ()2 {3HashTable HashTable ( -);4 5      for(inti =0; I < -; ++i)6 Hashtable.insertrecord (i);7 8 hashtable.print ();9 Tencout <<Endl; One  AHashtable.removerecord ( the); -Hashtable.removerecord ( -); -  the hashtable.print (); -  -     return 0; -}

Insert 0 to 99 keywords, hash to the table item size 13 in the hash list, delete the 91 and 702 key values.

The run results output a hash of 0 to 99 and a hash after the delete operation:

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[C + +] data structures for separating and linking the hash table