Create hash table in c

Programs/hash table in c

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+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#define SIZE 20
+
+struct DataItem {
+   int data;   
+   int key;
+};
+
+struct DataItem* hashArray[SIZE]; 
+struct DataItem* dummyItem;
+struct DataItem* item;
+
+int hashCode(int key) {
+   return key % SIZE;
+}
+
+struct DataItem *search(int key) {
+   //get the hash 
+   int hashIndex = hashCode(key);  
+
+   //move in array until an empty 
+   while(hashArray[hashIndex] != NULL) {
+
+      if(hashArray[hashIndex]->key == key)
+         return hashArray[hashIndex]; 
+
+      //go to next cell
+      ++hashIndex;
+
+      //wrap around the table
+      hashIndex %= SIZE;
+   }        
+
+   return NULL;        
+}
+
+void insert(int key,int data) {
+
+   struct DataItem *item = (struct DataItem*) malloc(sizeof(struct DataItem));
+   item->data = data;  
+   item->key = key;
+
+   //get the hash 
+   int hashIndex = hashCode(key);
+
+   //move in array until an empty or deleted cell
+   while(hashArray[hashIndex] != NULL && hashArray[hashIndex]->key != -1) {
+      //go to next cell
+      ++hashIndex;
+
+      //wrap around the table
+      hashIndex %= SIZE;
+   }
+
+   hashArray[hashIndex] = item;
+}
+
+struct DataItem* delete(struct DataItem* item) {
+   int key = item->key;
+
+   //get the hash 
+   int hashIndex = hashCode(key);
+
+   //move in array until an empty
+   while(hashArray[hashIndex] != NULL) {
+
+      if(hashArray[hashIndex]->key == key) {
+         struct DataItem* temp = hashArray[hashIndex]; 
+
+         //assign a dummy item at deleted position
+         hashArray[hashIndex] = dummyItem; 
+         return temp;
+      }
+
+      //go to next cell
+      ++hashIndex;
+
+      //wrap around the table
+      hashIndex %= SIZE;
+   }      
+
+   return NULL;        
+}
+
+void display() {
+   int i = 0;
+
+   for(i = 0; i<SIZE; i++) {
+
+      if(hashArray[i] != NULL)
+         printf(" (%d,%d)",hashArray[i]->key,hashArray[i]->data);
+      else
+         printf(" ~~ ");
+   }
+
+   printf("\n");
+}
+
+int main() {
+   dummyItem = (struct DataItem*) malloc(sizeof(struct DataItem));
+   dummyItem->data = -1;  
+   dummyItem->key = -1; 
+
+   insert(1, 20);
+   insert(2, 70);
+   insert(42, 80);
+   insert(4, 25);
+   insert(12, 44);
+   insert(14, 32);
+   insert(17, 11);
+   insert(13, 78);
+   insert(37, 97);
+
+   display();
+   item = search(37);
+
+   if(item != NULL) {
+      printf("Element found: %d\n", item->data);
+   } else {
+      printf("Element not found\n");
+   }
+
+   delete(item);
+   item = search(37);
+
+   if(item != NULL) {
+      printf("Element found: %d\n", item->data);
+   } else {
+      printf("Element not found\n");
+   }
+}