Program to implement Hash Table using Open Addressing

#include <stdio.h>

#include <stdlib.h>

  

struct HashNode {

    int key;

    int value;

};

  

const int capacity = 20;

int size = 0;

  

struct HashNode** arr;

struct HashNode* dummy;

  

void insert(int key, int V)

{

  

    struct HashNode* temp

        = (struct HashNode*)malloc(sizeof(struct HashNode));

    temp->key = key;

    temp->value = V;

  

    

    

    int hashIndex = key % capacity;

  

    

    while (arr[hashIndex] != NULL

           && arr[hashIndex]->key != key

           && arr[hashIndex]->key != -1) {

        hashIndex++;

        hashIndex %= capacity;

    }

  

    

    

    if (arr[hashIndex] == NULL

        || arr[hashIndex]->key == -1)

        size++;

  

    arr[hashIndex] = temp;

}

  

int delete (int key)

{

    

    

    int hashIndex = key % capacity;

  

    

    

    while (arr[hashIndex] != NULL) {

        

        if (arr[hashIndex]->key == key) {

            

            

            arr[hashIndex] = dummy;

  

            

            size--;

  

            

            return 1;

        }

        hashIndex++;

        hashIndex %= capacity;

    }

  

    

    return 0;

}

  

int find(int key)

{

    

    

    int hashIndex = (key % capacity);

  

    int counter = 0;

  

    

    while (arr[hashIndex] != NULL) {

  

        int counter = 0;

        

        

        if (counter++ > capacity)

            break;

  

        

        

        if (arr[hashIndex]->key == key)

            return arr[hashIndex]->value;

  

        hashIndex++;

        hashIndex %= capacity;

    }

  

    

    

    return -1;

}

  

int main()

{

    

    arr = (struct HashNode**)malloc(sizeof(struct HashNode*)

                                    * capacity);

    

    for (int i = 0; i < capacity; i++)

        arr[i] = NULL;

  

    dummy

        = (struct HashNode*)malloc(sizeof(struct HashNode));

  

    dummy->key = -1;

    dummy->value = -1;

  

    insert(1, 5);

    insert(2, 15);

    insert(3, 20);

    insert(4, 7);

  

    if (find(4) != -1)

        printf("Value of Key 4 = %d\n", find(4));

    else

        printf("Key 4 does not exists\n");

  

    if (delete (4))

        printf("Node value of key 4 is deleted "

               "successfully\n");

    else {

        printf("Key does not exists\n");

    }

  

    if (find(4) != -1)

        printf("Value of Key 4 = %d\n", find(4));

    else

        printf("Key 4 does not exists\n");

}

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