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Hash Table Program in C
Hash Table is a data structure which stores data in an associative manner. In hash table, the data is stored in an array format where each data value has its own unique index value. Access of data becomes very fast, if we know the index of the desired data.
Implementation in C
#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"); } }
If we compile and run the above program, it will produce the following result −
Output
~~ (1,20) (2,70) (42,80) (4,25) ~~ ~~ ~~ ~~ ~~ ~~ ~~ (12,44) (13,78) (14,32) ~~ ~~ (17,11) (37,97) ~~ Element found: 97 Element not found
hash_data_structure.htm
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