What Is Meant by Chaining in Data Structure?


Heather Bennett

Chaining in data structure refers to a method used to handle collisions in hash tables. When two or more elements are assigned to the same location (or bucket) within a hash table, chaining allows for the storage and retrieval of multiple values from that same location. This technique ensures that no data is lost and that all elements can be accessed efficiently.

How Does Chaining Work?

In a hash table, each data element is stored in an array-like structure called a bucket. The index of this bucket is determined by applying a hash function to the key of the element being inserted or searched for. However, different keys can sometimes produce the same hash value, leading to collisions.

To resolve collisions, chaining makes use of linked lists. Instead of storing only one element in each bucket, chaining allows multiple elements with the same hash value to be stored together as a linked list.

Insertion Process

When inserting an element into a hash table using chaining, the following steps are typically followed:

  1. The hash function is applied to the key of the new element.
  2. The resulting hash value determines which bucket will store the new element.
  3. If there are no elements already present at that location (an empty bucket), the new element is inserted as the head of a new linked list.
  4. If there are already existing elements in that bucket (a non-empty bucket), the new element is appended to the end of the linked list at that location.

Search Process

To search for an element using chaining, these steps are followed:

  1. The hash function is applied to the key of the element being searched.
  2. The resulting hash value is used to determine the bucket where the element should be located.
  3. The linked list at that bucket is traversed sequentially from start to end until either the desired element is found or the end of the list is reached.

Advantages of Chaining

Chaining offers several advantages when used as a collision resolution technique:

  • Simple Implementation: Chaining is relatively easy to implement compared to other collision resolution methods, such as open addressing or linear probing.
  • Space Efficiency: Chaining allows for efficient use of memory since it does not require a fixed-size array. The size of the hash table can dynamically grow or shrink as needed.
  • Fewer Clustering Issues: Unlike open addressing, chaining does not suffer from clustering issues, where elements tend to cluster around certain buckets, resulting in longer search times.

Disadvantages of Chaining

While chaining has its advantages, it also has some drawbacks:

  • Additional Memory Overhead: Chaining requires additional memory for storing pointers or references between elements within linked lists. This overhead can be significant when dealing with large numbers of elements or small-sized data types.
  • Inefficient Cache Usage: Since chained elements are stored in different memory locations, cache performance may suffer due to frequent cache misses during traversal of linked lists.

In conclusion, chaining in data structure provides an effective way to handle collisions in hash tables. It allows multiple elements with the same hash value to be stored in the same bucket using linked lists. While chaining is relatively easy to implement and offers space efficiency, it does come with additional memory overhead and potential cache performance issues.

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