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C++ Program to Implement Hash Tables 


  1. 

  2. #include<iostream>
  3. #include<cstdlib>
  4. #include<string>
  5. #include<cstdio>
  6. using namespace std;
  7. const int TABLE_SIZE = 128;
  8.  
  9. /*
  10.  * HashEntry Class Declaration
  11.  */
  12. class HashEntry
  13. {
  14.     public:
  15.         int key;
  16.         int value;
  17.         HashEntry(int key, int value)
  18.         {
  19.             this->key = key;
  20.             this->value = value;
  21.         }
  22. };
  23.  
  24. /*
  25.  * HashMap Class Declaration
  26.  */
  27. class HashMap
  28. {
  29.     private:
  30.         HashEntry **table;
  31.     public:   
  32.         HashMap()
  33.  {
  34.             table = new HashEntry * [TABLE_SIZE];
  35.             for (int i = 0; i< TABLE_SIZE; i++)
  36.             {
  37.                 table[i] = NULL;
  38.             }
  39.         }
  40.         /*
  41.          * Hash Function
  42.          */
  43.         int HashFunc(int key)
  44.         {
  45.             return key % TABLE_SIZE;
  46.         }
  47.         /*
  48.          * Insert Element at a key
  49.          */
  50.  void Insert(int key, int value)
  51.  {
  52.             int hash = HashFunc(key);
  53.             while (table[hash] != NULL && table[hash]->key != key)
  54.             {
  55.                 hash = HashFunc(hash + 1);
  56.             }
  57.             if (table[hash] != NULL)
  58.                 delete table[hash];
  59.             table[hash] = new HashEntry(key, value);
  60.  }
  61.         /*
  62.          * Search Element at a key
  63.          */
  64.         int Search(int key)
  65.  {
  66.      int  hash = HashFunc(key);
  67.      while (table[hash] != NULL && table[hash]->key != key)
  68.      {
  69.          hash = HashFunc(hash + 1);
  70.      }
  71.      if (table[hash] == NULL)
  72.          return -1;
  73.      else
  74.          return table[hash]->value;
  75.         }
  76.  
  77.         /*
  78.          * Remove Element at a key
  79.          */
  80.         void Remove(int key)
  81.  {
  82.      int hash = HashFunc(key);
  83.      while (table[hash] != NULL)
  84.      {
  85.          if (table[hash]->key == key)
  86.              break;
  87.          hash = HashFunc(hash + 1);
  88.      }
  89.             if (table[hash] == NULL)
  90.      {
  91.                 cout<<"No Element found at key "<<key<<endl;
  92.                 return;
  93.             }
  94.             else
  95.             {
  96.                 delete table[hash];
  97.             }
  98.             cout<<"Element Deleted"<<endl;
  99.         }
  100.         ~HashMap()
  101.  {
  102.             for (int i = 0; i < TABLE_SIZE; i++)
  103.             {
  104.                 if (table[i] != NULL)
  105.                     delete table[i];
  106.                 delete[] table;
  107.             }
  108.         }
  109. };
  110. /*
  111.  * Main Contains Menu
  112.  */
  113. int main()
  114. {
  115.     HashMap hash;
  116.     int key, value;
  117.     int choice;
  118.     while (1)
  119.     {
  120.         cout<<"\n----------------------"<<endl;
  121.         cout<<"Operations on Hash Table"<<endl;
  122.         cout<<"\n----------------------"<<endl;
  123.         cout<<"1.Insert element into the table"<<endl;
  124.         cout<<"2.Search element from the key"<<endl;
  125.         cout<<"3.Delete element at a key"<<endl;
  126.         cout<<"4.Exit"<<endl;
  127.         cout<<"Enter your choice: ";
  128.         cin>>choice;
  129.         switch(choice)
  130.         {
  131.         case 1:
  132.             cout<<"Enter element to be inserted: ";
  133.             cin>>value;
  134.             cout<<"Enter key at which element to be inserted: ";
  135.             cin>>key;
  136.             hash.Insert(key, value);
  137.             break;
  138.         case 2:
  139.             cout<<"Enter key of the element to be searched: ";
  140.             cin>>key;
  141.             if (hash.Search(key) == -1)
  142.             {
  143.          cout<<"No element found at key "<<key<<endl;
  144.          continue;
  145.      }
  146.      else
  147.      {
  148.          cout<<"Element at key "<<key<<" : ";
  149.          cout<<hash.Search(key)<<endl;
  150.      }
  151.             break;
  152.         case 3:
  153.             cout<<"Enter key of the element to be deleted: ";
  154.             cin>>key;
  155.             hash.Remove(key);
  156.             break;
  157.         case 4:
  158.             exit(1);
  159.         default:
  160.            cout<<"\nEnter correct option\n";
  161.        }
  162.     }
  163.     return 0;
  164. }

OUTPUT

Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 12
Enter key at which element to be inserted: 1

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 24
Enter key at which element to be inserted: 2

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 36
Enter key at which element to be inserted: 3

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 48
Enter key at which element to be inserted: 4

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 1
Enter element to be inserted: 60
Enter key at which element to be inserted: 5

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 3
Element at key 3 : 36

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 5
Element at key 5 : 60

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 3
Enter key of the element to be deleted: 4
Element Deleted

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 4
No element found at key 4

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 2
Enter key of the element to be searched: 2
Element at key 2 : 24

----------------------
Operations on Hash Table

----------------------
1.Insert element into the table
2.Search element from the key
3.Delete element at a key
4.Exit
Enter your choice: 4
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