Double Hashing: C program

Algorithm to insert a value in Double hashing

Hashtable is an array of size = TABLE_SIZE

Step 1: Read the value to be inserted,key

Step 2:  let i = 0

Step 3: Let R be the nearest prime < TABLE_SIZE

Step 4: hkey=key%TABLE_SIZE;
 hash2 = 7-(key %7);
Step 5: compute the index at which the value has to be inserted in hash table

                 index=(hkey+i*hash2)%TABLE_SIZE;

Step 6: if there is no element at that index then  insert the value at index and STOP

Step 7: If there is already an element at that index

                step 6.1: i = i+1

step 8:  if i < TABLE_SIZE then go to step 5

Algorithm to search a value in Double Hashing

Hashtable is an array of size = TABLE_SIZE

Step 1: Read the value to be searched, key

Step 2:  let i = 0

Step 3: Let R be the nearest prime < TABLE_SIZE

Step 4:  hkey=key%TABLE_SIZE;
 hash2 = 7-(key %7);
Step 5: compute the index at which the value can be found

             index=(hkey+i*hash2)%TABLE_SIZE;

Step 6: if the  element at that index is same as the search value then print element found and  STOP

Step 7: If there is already an element at that index

                step 6.1: i = i+1

step 8:  if i < TABLE_SIZE then go to step 5

 


#include <stdio.h>
#include<stdlib.h>
#define TABLE_SIZE 10

int h[TABLE_SIZE]={NULL};

void insert()
{

 int key,index,i,flag=0,hkey,hash2;
 printf("\nenter a value to insert into hash table\n");
 scanf("%d",&key);
 hkey=key%TABLE_SIZE;
 hash2 = 7-(key %7);
 for(i=0;i<TABLE_SIZE;i++)
 {
    index=(hkey+i*hash2)%TABLE_SIZE;
    if(h[index] == NULL)
    {
        h[index]=key;
        break;
    }
 }
 if(i == TABLE_SIZE)
     printf("\nelement cannot be inserted\n");
}
void search()
{

 int key,index,i,flag=0,hash2,hkey;
 printf("\nenter search element\n");
 scanf("%d",&key);
  hkey=key%TABLE_SIZE;
 hash2 = 7-(key %7);
 for(i=0;i<TABLE_SIZE; i++)
 {
    index=(hkey+i*hash2)%TABLE_SIZE;
    if(h[index]==key)
    {
      printf("value is found at index %d",index);
      break;
    }
  }
  if(i == TABLE_SIZE)
    printf("\n value is not found\n");
}
void display()
{

  int i;
  printf("\nelements in the hash table are \n");
  for(i=0;i< TABLE_SIZE; i++)
    printf("\nat index %d \t value =  %d",i,h[i]);

}
main()
{
    int opt,i;
    while(1)
    {
        printf("\nPress 1. Insert\t 2. Display \t3. Search \t4.Exit \n");
        scanf("%d",&opt);
        switch(opt)
        {
            case 1:
                insert();
                break;
            case 2:
                display();
                break;
            case 3:
                search();
                break;
            case 4:exit(0);
        }
    }
}



Output
Press 1. Insert     2. Display     3. Search     4.Exit
1

enter a value to insert into hash table
12

Press 1. Insert     2. Display     3. Search     4.Exit
1

enter a value to insert into hash table
22

Press 1. Insert     2. Display     3. Search     4.Exit
1

enter a value to insert into hash table
32

Press 1. Insert     2. Display     3. Search     4.Exit
2

elements in the hash table are

at index 0      value =  0
at index 1      value =  0
at index 2      value =  12
at index 3      value =  0
at index 4      value =  0
at index 5      value =  32
at index 6      value =  0
at index 7      value =  0
at index 8      value =  22
at index 9      value =  0
Press 1. Insert     2. Display     3. Search     4.Exit
3

enter search element
22
value is found at index 8
Press 1. Insert     2. Display     3. Search     4.Exit
3

enter search element
34

 value is not found

Press 1. Insert     2. Display     3. Search     4.Exit
4