public/subjects/how_many_references

how many references

Instructions

Create the following functions :

• add_ele that adds an element to the value in the Node
• how_many_references that returns how many times the value is referenced in the code
• rm_all_ref that receives a Rc<String> and removes all elements from the vector that are equal to that value, this should only happen if the two Rcs point to the same allocation

Expected Function

pub use std::rc::Rc;

pub struct Node {
    pub value: Vec<Rc<String>>,
}

impl Node {
    pub fn new(value: Vec<Rc<String>>) -> Node {
        Node { value: value }
    }
    pub fn add_ele(&mut self, v: Rc<String>) {}
    pub fn rm_all_ref(&mut self, v: Rc<String>) {}
}

pub fn how_many_references(value: &Rc<String>) -> usize {}

Usage

Here is a program to test your function

fn main() {
    let a = Rc::new(String::from("a"));
    let b = Rc::new(String::from("b"));
    let c = Rc::new(String::from("c"));

    let a1 = Rc::new(String::from("a"));

    let mut new_node = Node::new(vec![a.clone()]);
    new_node.add_ele(b.clone());
    new_node.add_ele(a.clone());
    new_node.add_ele(c.clone());
    new_node.add_ele(a.clone());

    println!("a: {:?}", how_many_references(&a));
    println!("b: {:?}", how_many_references(&b));
    println!("c: {:?}", how_many_references(&c));
    new_node.rm_all_ref(a1.clone());
    new_node.rm_all_ref(a.clone());

    println!("a: {:?}", how_many_references(&a));
    println!("b: {:?}", how_many_references(&b));
    println!("c: {:?}", how_many_references(&c));
}

And its output:

student@ubuntu:~/[[ROOT]]/test$ cargo run
a: 4
b: 2
c: 2
a: 1
b: 2
c: 2
student@ubuntu:~/[[ROOT]]/test$

Notions

• https://doc.rust-lang.org/book/ch15-04-rc.html
• https://doc.rust-lang.org/std/rc/struct.Rc.html