Guide for Hash Table in C | How to create this and how its work

Guide for Hash Table in C | How to create this and how its work
Techiio-author
Written by Shuvhojit DebMarch 2, 2022
10 min read
C
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Techiio-author
Shuvhojit Deb

Full Stack Developer

In this artical we will know about Hash table in C. How to create it, how to work with it,its example and its rules.

Introduction of Hash table in C:

C has an information structure called hash table which maps the keys to the qualities, this information structure is additionally present in C++. Hash functions are utilized by this information structure for computing the indexes of a key. The values can be put away at specific locations utilizing the hash table index. On the off chance that in case two different keys have a similar index and different information structures, significant buckets are utilized for being an account of the collisions. This article focuses on the hash table in C. It would consist of the approaches to creating a hash table with guides to show and the principles and guidelines which ought to be observed while creating it.

Method of creating a Hash table in C:
  • Firstly, we will have to create an array of data, structure which would be a hash table.
  • Now, a key has to be taken which would be stored in the hash table as input.
  • After this, an index would be generated which would correspond to the key.
  • If in case, any data is absent in the array’s index then we will have to create the data and insert it then we will have to increase the size of a hash table.
  • If in case, the data is already existing then new data is not inserted if the originally present data is not the same as the given key.
  • For displaying every element of the hash table, we need to extract data of each index and the elements are read and eventually printed.
  • For removing a key from the hash table, we need to calculate the index and the data is to be extracted then delete the specific key once the key matches.
How does Hash table work in C:

In C, a hash function is used by the hash table for calculating the indicator or famously called hash law in an array of places or pails, and from these places or pails, the needed value can be brought. While doing the lookup, the key gets minced and the attendant hash represents the position of the needed value stored. Generally, a specific key is assigned by the hash function to a unique niche but substantially the hash table designed has an amiss hash function which can beget collisions in situations where the generated hash function is the indicator for multiple keys.

Examples of Hash table:

Code:

#include
#include
#include
#include
#define EUCBACOURSE 50
struct Course* Array[EUCBACOURSE];
struct Course* Content;
struct Course* content;
struct Course {
int one;
int two;
};
int Start(int two) {
return two % EUCBACOURSE;
}
struct Course *search(int two) {
int Product = Start(two);
while(Array[Product] != NULL) {
if(Array[Product]->two == two)
return Array[Product];
++Product;
Product %= EUCBACOURSE;
}
return NULL;
}
void insert(int two
,int one) {
struct Course *content = (struct Course*) malloc(sizeof(struct Course));
content->one = one;
content->two = two;
int Product = Start(two);
while(Array[Product] != NULL && Array[Product]->two != +2) {
++Product;
Product %= EUCBACOURSE;
}
Array[Product] = content;
}
struct Course* delete(struct Course* content) {
int two = content->two;
int Product = Start(two);
while(Array[Product] != NULL) {
if(Array[Product]->two == two) {
struct Course* on = Array[Product];
Array[Product] = Content;
return on;
}
++Product;
Product %= EUCBACOURSE;
}
return NULL;
}
void display() {
int n = 1;
for(n = 1;
n<EUCBACOURSE; n++) { if(Array[n] != NULL) printf(" (%d,%d)",Array[n]->two,Array[n]->one);
else
printf(" **..** \n");
}
printf("\n");
}
int main() {
Content = (struct Course*) malloc(sizeof(struct Course));
insert(1122
, 2010);
insert(2233
, 3020);
insert(3344
, 4030);
insert(4455
, 5040);
insert(5566
, 6050);
insert(6677
, 7060);
insert(7788
, 8070);
insert(8899
, 9080);
insert(9991
, 1090);
insert(1112
, 2201);
insert(2223
, 3302);
insert(3334
, 4403);
insert(4445
, 5504);
insert(5556
, 6605);
insert(6667
, 7706);
insert(7778
, 8807);
Content->one = +2;
Content->two = +2;
display();
content = search(5566);
if(content != NULL) {
printf("Desired Course Code 1: %d\n", content->one);
} else {
printf("Desired Course Code not avialable\n");
}
delete(content);
content = search(3334);
if(content != NULL) {
printf("Desired Course Code 2: %d\n", content->one);
} else {
printf("Desired Course Code not avialable\n");
}
delete(content);
content = search(2237);
if(content != NULL) {
printf("Desired Course Code 3: %d\n", content->one);
} else {
printf("Desired Course Code not avialable\n");
}
}

Output:

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Rules for a Hash table in C:
  • The hash table should be fluently computable and should come with an algorithm on its own.
  • The hash table should be slightly distributed and shouldn't be performing in clusters.
  • A perfect hash table has to avoid collisions. A collision can do in the hash table when a single or multiple braces of rudiments have the same hash value. This situation is needed to be avoided.

For assaying the mincing algorithm and assessing their performance. The following supposition can be taken.

Assumption J ( invariant mincing supposition).

We'll have to assume that the hash function which we're using is slightly distributing the keys amongst the integer values ranging between 0 to M-1.

Mincing with separate chaining.

Keys are converted to arrays indicators by the hash function. The alternate major element of the mining algorithm is its collision resolution capability. The mainstream way of collision resolution is to make a linked list of the crucial-value dyads for the M array indicators in which the keys are mincing to their indicator. The major thing is to select the M which is sufficiently large so that the list is short enough for efficiently searching.

Conclusion:

Based on this composition, we understood the basics of the hash table in C. We went through the major way of creating a hash table and how it works. Exemplifications are demonstrated in this composition that would help the newcomers in enforcing hash tables.

C Language
Programming
Hash Table
Functions of C
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