Substrings

📌 Overview

This project implements a Ruby method that takes a string and a dictionary of words, then counts how many times each dictionary word appears as a substring within the given string.

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🧠 Problem Description

Given:

• A string (sentence or phrase)
• A dictionary (array of words)

The method should return a hash where:

• The keys are the words from the dictionary
• The values are the number of times each word appears as a substring in the string

The comparison is case-insensitive.

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🧩 Example

string = "Howdy partner, sit down! How's it going?"
dictionary = ["how", "down", "go", "it", "partner"]

Expected output:

{
  "how" => 2,
  "partner" => 1,
  "down" => 1,
  "go" => 1,
  "it" => 2
}

📌 Notes:

• Substrings can appear inside larger words
• Matching is not limited by word boundaries
• Case differences are ignored

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✨ Features

• Case-insensitive matching
• Counts multiple occurrences of the same substring
• Works with punctuation and symbols in the input string
• Simple and readable Ruby implementation

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🛠️ Implementation

The main method signature:

def substrings(string, dictionary)

Parameters

• string → the input text to be analyzed
• dictionary → an array of words to search for

Return value

• A hash containing each found substring and its occurrence count

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🧪 Testing

The project can be tested using RSpec.

Test cases typically cover:

• Case-insensitive matches
• Multiple occurrences of the same substring
• Substrings inside larger words
• Inputs with punctuation and spaces

To run the tests:

rspec

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⏱️ Algorithm Complexity

• Time Complexity: O(n × m), where:

  • n is the number of words in the dictionary
  • m is the length of the input string

• Space Complexity: O(k), where k is the number of matched substrings stored in the hash

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🧹 Code Style

This project follows standard Ruby style guidelines:

• 2-space indentation
• Clear and descriptive variable names
• Small, readable methods
• Emphasis on clarity over cleverness

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💎 Language

• Ruby

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🎓 Origin

This project is part of The Odin Project Ruby curriculum and was developed as a learning exercise to strengthen understanding of strings, hashes, and basic algorithm design.