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Crochemore-Perrin

Crochemore-Perrin addresses exact string matching by applying two-way matching with maximal suffix computation.

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Quick Facts

Compact metadata for implementation and discovery.

Category: Pattern Matching
Difficulty: Intermediate
Family: Exact String Matching
Tier: Extended
Status: Verified
Review: Source Checked
Sources: 1
Formulas: 0
Relationships: 3
Code example: Ready
Visualization: Ready

Overview

Crochemore-Perrin is a exact string matching method for exact string matching. It works by applying two-way matching with maximal suffix computation.

Core Concepts

exact string matchingmatchingsuffix structurepattern matching

Quick facts

Complexity

Runtime and memory behavior at a glance.

Best

O(n)

Average

O(n + m)

Worst

O(n + m)

Space

O(n + m)

When to Use

Use Crochemore-Perrin when solving exact string matching and you want to benefit from applying two-way matching with maximal suffix computation.
Choose it when O(n + m) average/worst-case time and O(n + m) memory match your workload profile.
Prefer it over Bit-Parallel Levenshtein or Shift-And Algorithm when the problem structure favors exact string matching.

When Not to Use

Avoid when preprocessing cost is larger than the savings for a one-off tiny input.
Avoid when the alphabet or scoring assumptions do not match the sequence data.

What It Does

Computes exact string matching within Exact String Matching workloads (O(n + m) time, O(n + m) space).
Works by applying two-way matching with maximal suffix computation.
Maintains key invariants across exact string matching, matching, suffix structure.

Use Cases

Production and research workloads requiring exact string matching via applying two-way matching with maximal suffix computation.
Exact String Matching pipelines where O(n + m) time and O(n + m) space fit system constraints.
Engineering comparisons against Bit-Parallel Levenshtein and Shift-And Algorithm when tuning exact string matching.

Inputs

Text or sequence
Pattern, index, or comparison sequence

Outputs

Matches, alignment, index, or similarity value

Pseudocode

1.Preprocess the input alphabet, pattern/grammar rules, or symbol frequency tables for Crochemore-Perrin.
2.Construct the lookup automaton, suffix/shift index, or coding state (exact string matching, matching).
3.Scan the input sequence by applying two-way matching with maximal suffix computation.
4.Emit matches, derivation nodes, or encoded tokens while advancing the state transition table.
5.Finalize trailing state and return the completed exact string matching output.

Canonical Example

Input: Text or sequence configured for a representative exact string matching test case
Output: Matches, alignment, index, or similarity value satisfying Crochemore-Perrin invariants
Explanation: Crochemore-Perrin processes the input by applying two-way matching with maximal suffix computation, tracking exact string matching and matching to produce the verified exact string matching result.

Implementation Notes

Keep preprocessing output inspectable with short examples.
Test repeated characters and overlapping matches.
Document sentinel or alphabet assumptions.

Common Pitfalls

Mishandling empty patterns, repeated characters, or sentinel symbols.
Confusing preprocessing indexes with the query algorithm.
Forgetting whether indexing is zero-based or one-based.

Interactive Mechanism Walkthrough

Sequence Window & Automaton Alignment

Show applying two-way matching with maximal suffix computation on a small exact string matching example.

Input:ABABABCABAB

Window:ABAB

Step 1 of 5: Preprocess the input alphabet, pattern/grammar rules, or symbol frequency tables for Crochemore-Perrin.

pattern-matching-mechanism

Notes

Crochemore-Perrin operates in O(n + m) time and O(n + m) space within the Exact String Matching family. Often compared with Bit-Parallel Levenshtein and Shift-And Algorithm.