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Now that we know about vectors and hashmaps, let’s tackle something more challenging. In this exercise, we’ll build a system to manage and analyze student grades. This challenge will help you practice working with structs, hashmaps, vectors, and methods while managing a collection of data.

The focus here is on functionality. Ignore error handling for this challenge; assume the input is always valid.

Your Task

You need to define the StudentGrades struct, which contains a HashMap of student names (String) as keys and Student structs as values. Each Student struct should have the following fields:

  • name: The name of the student (String).
  • grades: A Vec<u8> to store the student's grades.

Implement the following methods for the StudentGrades struct:

  1. add_student(name: &str): Add a new student to the HashMap. If the student already exists, do nothing.
  2. add_grade(name: &str, grade: u8): Add a grade to an existing student.
  3. get_grades(name: &str) -> &[u8]: Retrieve the grades of a student as an immutable reference.
  4. Since there’s no error handling, assume all inputs are valid, and keys will exist when accessed.

Hints

<details> <summary>Click here to reveal hints</summary>
  • Use the HashMap methods like entry, insert, and get to manage student data.
</details>
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use std::collections::HashMap;


pub struct Student {
    // 1. Define the fields
}


pub struct StudentGrades {
    // 2. Define the fields
}


impl StudentGrades {
    pub fn new() -> Self {
        Self {
            students: HashMap::new(),
        }
    }


    // 3. Implement the methods
    pub fn add_student(&mut self, name: &str) {
        // Implement here
    }


    pub fn add_grade(&mut self, name: &str, grade: u8) {
        // Implement here
    }


    pub fn get_grades(&self, name: &str) -> &[u8] {
        // Implement here
    }
}


// Example usage
pub fn main() {
    let mut tracker = StudentGrades::new();


    tracker.add_student("Alice");
    tracker.add_student("Bob");


    tracker.add_grade("Alice", 85);
    tracker.add_grade("Alice", 90);
    tracker.add_grade("Bob", 78);


    println!("{:?}", tracker.get_grades("Alice")); // [85, 90]
    println!("{:?}", tracker.get_grades("Bob")); // [78]
}