Rabin-Karp

Rabin-Karp Algorithm: The Rabin-Karp algorithm is a string matching algorithm used to find a given pattern in a text. It is a variation of the Knuth-Morris-...

Rabin-Karp Algorithm:

The Rabin-Karp algorithm is a string matching algorithm used to find a given pattern in a text. It is a variation of the Knuth-Morris-Pratt algorithm and is considered efficient for large pattern sizes.

Key Concepts:

Pattern: The string to be matched.
Text: The text to search for the pattern.
Hash Function: A function that maps the pattern to a unique index in the text.
Hash Value: The result of the hash function applied to the pattern.

Algorithm:

Initialization:

The algorithm starts by setting up two variables, p and q, which represent the lengths of the pattern and the text, respectively.
The hash function is then used to calculate the hash value for the pattern.
i and j are initialized to 0, representing the start and end positions of the pattern in the text.

Matching:

For each character in the text, the algorithm calculates the hash value of the pattern starting from that position.
If the hash values match the stored hash value, it means a match is found.
The algorithm updates the start position i to the next character in the text.

Termination:

If no match is found during the search, the algorithm terminates, indicating that the pattern is not present in the text.

Example:

Suppose we have the following pattern: "abc"

And the following text: "cabcabc"

The hash function would be applied to the pattern, resulting in the hash value "abc".

The algorithm would then iterate over the text and calculate the hash values for each character.

If the hash value matches "abc", a match is found at positions 2 and 4.

The algorithm would then update the start position to 3 and continue searching for a match.

No match is found, so the algorithm terminates