JUHU

Cargo.toml

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+[package]
+name = "linked-list"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+# Not needed :D

src/main.rs

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+/// This is not a very beautiful solution!
+///
+/// This was just created for understanding the concept and trying it out.
+
+#[derive(Debug)]
+struct ListItem {
+    value: String,
+    next: Option<Box<ListItem>>
+}
+
+impl ListItem {
+    fn new(value: String) -> ListItem {
+        ListItem {
+            value,
+            next: None
+        }
+    }
+}
+
+#[derive(Debug)]
+struct List {
+    head: Option<Box<ListItem>>,
+}
+
+impl List {
+    /// create an empty list
+    fn new() -> List {
+        List { head: None }
+    }
+
+    /// push a [ListItem] onto the list
+    fn push(&mut self, item: ListItem) {
+        let prev_head = self.head.take();
+        let mut new_head = Box::new(item);
+        new_head.next = prev_head;
+        self.head = Some(new_head);
+    }
+
+    /// returns None if there is no top item
+    fn pop(&mut self) -> Option<()> {
+        // TODO: return removed item
+        let head = self.head.take();
+        self.head = head?.next;
+        Some(())
+    }
+
+    /// Returns None if len > u64
+    fn len(&self) -> Option<usize> {
+        let mut num: usize = 0;
+        if let Some(curr) = &self.head {
+            // create a mutable reference so we don't actually manipulate the data
+            let mut curr = curr;
+            num = num.checked_add(1)?;
+            while curr.next.is_some() {
+                curr = curr.next.as_ref().unwrap();
+                num = num.checked_add(1)?;
+            }
+        }
+        Some(num)
+    }
+}
+
+fn main() {
+    let mut list = List::new();
+
+    list.push(ListItem::new("Test".to_owned()));
+    list.push(ListItem::new("Test2".to_owned()));
+    list.push(ListItem::new("Test3".to_owned()));
+
+    println!("len: {:?}", list.len());
+    dbg!(&list);
+
+    list.pop();
+
+    println!("len: {:?}", list.len());
+    dbg!(&list);
+}