Author: Rudi Cilibrasi

Given a text file containing words in each line, output all unique words in an alphabetical order and list all the lines they appear in. If any of them appears in a single line more than one then only print the line number once for it. Also, the line numbers in which each word appeared should be sorted in increasing order.

To effectively tackle this problem, it is important to have a basic understanding of the following concepts:

1. Rust Syntax: Familiarity with Rust's syntax, including functions, control flow, and data structures.
2. Ownership and Borrowing: Understanding Rust’s ownership model is crucial for memory safety and efficient resource management.
3. Data Structures: Knowledge of BTreeMap and BTreeSet for organizing unique words and their occurrences.
4. String Manipulation: Skills in manipulating strings and working with slices.
5. File I/O: Understanding how to read from files and handle command-line arguments.

1. read_file(file_path: &str) -> Result<String, std::io::Error>
   Reads the contents of a specified file and returns it as a String.

2. get_lines_lower_case(text: &str) -> Vec<String>
   Converts the input text to lowercase and splits it into lines, returning a vector of strings.

3. solve(content: &str) -> BTreeMap<String, BTreeSet<usize>>
   Processes the content of the text, identifying unique words and mapping them to the line numbers where they appear.

4. read_file_from_args() -> Result<String, std::io::Error>
   Reads the file input from command-line arguments.

Given the input text:

Apple banana cherry
Banana dog cat
Rust is a programming language
Hello world from Rust
The quick brown fox jumps
The lazy dog is cute
This is a test file
For testing random purposes
Banana and apple are fruits
Goodbye and hello

The output will be:

Word: 'a', Lines: {3, 7}
Word: 'and', Lines: {9, 10}
Word: 'apple', Lines: {1, 9}
Word: 'are', Lines: {9}
Word: 'banana', Lines: {1, 2, 9}
Word: 'brown', Lines: {5}
Word: 'cat', Lines: {2}
Word: 'cherry', Lines: {1}
Word: 'cute', Lines: {6}
Word: 'dog', Lines: {2, 6}
Word: 'file', Lines: {7}
Word: 'for', Lines: {8}
Word: 'fox', Lines: {5}
Word: 'from', Lines: {4}
Word: 'fruits', Lines: {9}
Word: 'goodbye', Lines: {10}
Word: 'hello', Lines: {4, 10}
Word: 'is', Lines: {3, 6, 7}
Word: 'jumps', Lines: {5}
Word: 'language', Lines: {3}
Word: 'lazy', Lines: {6}
Word: 'programming', Lines: {3}
Word: 'purposes', Lines: {8}
Word: 'quick', Lines: {5}
Word: 'random', Lines: {8}
Word: 'rust', Lines: {3, 4}
Word: 'test', Lines: {7}
Word: 'testing', Lines: {8}
Word: 'the', Lines: {5, 6}
Word: 'this', Lines: {7}
Word: 'world', Lines: {4}

To run the parser on an input file, use the following command in your terminal:

cargo run -- ./input/small.txt