Implement Hash Tables Using Chaining with Singly Linked Lists in C++

A hash table is a data structure which is used to store key-value pairs. Hash function is used by hash table to compute an index into an array in which an element will be inserted or searched.

This is a C++ program to Implement Hash Tables chaining with singly linked lists.

Algorithm

For insert:

Begin    Declare Function Insert(int k, int v)       int hash_v = HashFunc(k)       HashTableEntry* p = NULL       HashTableEntry* en = ht[hash_v]       while (en!= NULL)          p = en          en= en->n       if (en == NULL)          en = new HashTableEntry(k, v)          if (p == NULL)             ht[hash_v] = en          else             p->n= en       else          en->v = v End.

For delete:

Begin    Declare Function Remove(int k)       int hash_v = HashFunc(k)       HashTableEntry* en = ht[hash_v]       HashTableEntry* p= NULL       if (en == NULL or en->k != k)          Print “No Element found at key”          return       while (en->n != NULL)          p = en          en = en->n       if (p != NULL)          p->n = en->n       delete en          Print “Element Deleted” End.

For Search a key value:

Begin    Declare function SearchKey(int k)       int hash_v = HashFunc(k)       bool flag = false       HashTableEntry* en = ht[hash_v]       if (en != NULL)          while (en != NULL)             if (en->k == k)                flag = true             if (flag)                Print “Element found at key”                Print en->v             en = en->n       if (!flag)          Print “No Element found at key” End.

Example Code

 Live Demo

#include <iostream> const int T_S = 200; using namespace std; struct HashTableEntry {    int v, k;    HashTableEntry *n;    HashTableEntry *p;    HashTableEntry(int k, int v) {       this->k = k;       this->v = v;       this->n = NULL;    } }; class HashMapTable {    public:       HashTableEntry **ht, **top;       HashMapTable() {          ht = new HashTableEntry*[T_S];          for (int i = 0; i < T_S; i++)             ht[i] = NULL;       }       int HashFunc(int key) {          return key % T_S;       }       void Insert(int k, int v) {          int hash_v = HashFunc(k);          HashTableEntry* p = NULL;          HashTableEntry* en = ht[hash_v];          while (en!= NULL) {             p = en;             en = en->n;          }          if (en == NULL) {             en = new HashTableEntry(k, v);             if (p == NULL) {                ht[hash_v] = en;             } else {                p->n = en;             }          } else {             en->v = v;          }       }       void Remove(int k) {          int hash_v = HashFunc(k);          HashTableEntry* en = ht[hash_v];          HashTableEntry* p = NULL;          if (en == NULL || en->k != k) {             cout<<"No Element found at key "<<k<<endl;             return;          }          while (en->n != NULL) {             p = en;             en = en->n;          }          if (p != NULL) {             p->n = en->n;          }          delete en;          cout<<"Element Deleted"<<endl;       }       void SearchKey(int k) {          int hash_v = HashFunc(k);          bool flag = false;          HashTableEntry* en = ht[hash_v];          if (en != NULL) {             while (en != NULL) {                if (en->k == k) {                   flag = true;                }                if (flag) {                   cout<<"Element found at key "<<k<<": ";                   cout<<en->v<<endl;                }                en = en->n;             }          }          if (!flag)             cout<<"No Element found at key "<<k<<endl;       }       ~HashMapTable() {          delete [] ht;       } }; int main() {    HashMapTable hash;    int k, v;    int c;    while (1) {       cout<<"1.Insert element into the table"<<endl;       cout<<"2.Search element from the key"<<endl;       cout<<"3.Delete element at a key"<<endl;       cout<<"4.Exit"<<endl;       cout<<"Enter your choice: ";       cin>>c;       switch(c) {          case 1:             cout<<"Enter element to be inserted: ";             cin>>v;             cout<<"Enter key at which element to be inserted: ";             cin>>k;             hash.Insert(k, v);          break;          case 2:             cout<<"Enter key of the element to be searched: ";             cin>>k;             hash.SearchKey(k);          break;          case 3:             cout<<"Enter key of the element to be deleted: ";             cin>>k;             hash.Remove(k);          break;          case 4:             exit(1);          default:             cout<<"\nEnter correct option\n";       }    }    return 0; }

Output

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: 2 Enter key at which element to be inserted: 1 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: 3 Enter key at which element to be inserted: 4 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: 7 Enter key at which element to be inserted: 6 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: 8 Enter key at which element to be inserted: 9 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: 6 Element found at key 6: 7 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: 7 No Element found at key 7 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: 9 Element Deleted 1.Insert element into the table 2.Search element from the key 3.Delete element at a key 4.Exit Enter your choice: 4