Exact String Matching in Text

Exact string matching is a process of finding occurrences of a pattern string within a larger text string. It involves comparing the pattern string with substrings of the text to determine if there is a match.

Rabin-Karp Algorithm
The Rabin-Karp algorithm is a string searching algorithm that uses hashing to find exact string matches in a text. It is efficient for searching patterns in large texts and has an average case time complexity of O(n+m), where n is the length of the text and m is the length of the pattern.

Algorithm Steps:
1. Calculate the hash value of the pattern string.
2. Calculate the hash value of the first substring of the same length from the text.
3. Compare the hash values. If they match, perform a character-by-character comparison to verify the match.
4. If there is no match, slide the pattern by one character and recalculate the hash value of the new substring.
5. Repeat steps 3 and 4 until a match is found or the end of the text is reached.

Hash Function:
The Rabin-Karp algorithm uses a rolling hash function, which allows the hash value of a substring to be efficiently calculated based on the previous substring's hash value. This helps in avoiding unnecessary recalculations of hash values.

Advantages of Rabin-Karp Algorithm:
- It efficiently handles cases where the pattern and text have a large alphabet size.
- It does not require preprocessing of the pattern string.
- It can handle multiple pattern matches efficiently.

Disadvantages of Rabin-Karp Algorithm:
- It may produce false positive matches due to hash collisions.
- It requires additional checks for false positives using character-by-character comparisons.

Conclusion
The Rabin-Karp algorithm is a widely used string searching algorithm for exact string matching in a text. It utilizes hashing and rolling hash functions to efficiently search for patterns. While it has some limitations, it is a powerful algorithm for handling various string matching scenarios.