023 透過連結串列學Rust之非安全方式實現連結串列1

linghuyichong發表於2021-07-11
Rust

影片地址：www.bilibili.com/video/av78062009/
相關原始碼：github.com/anonymousGiga/Rust-link...

我們重新定義連結串列如下：

pub struct List<T> {
    head: Link<T>,
    tail: *mut Node<T>,
}

type Link<T> = Option<Box<Node<T>>>;

struct Node<T> {
    elem: T,
    next: Link<T>,
}
    pub fn new() -> Self {
        List { head: None, tail: ptr::null_mut() }
    }

下面我們來實現push，程式碼如下：

    pub fn push(&mut self, elem: T)     {
        let mut new_tail = Box::new(Node {
            elem: elem,
            next: None,
        });

        let raw_tail: *mut _ = &mut *new_tail;

        if !self.tail.is_null() {
            unsafe {//非安全程式碼
                (*self.tail).next = Some(new_tail);
            }
        } else {
            self.head = Some(new_tail);
        }

        self.tail = raw_tail;
    }

下面我們來實現pop，實現程式碼如下：

    pub fn pop(&mut self) -> Option<T> {
        self.head.take().map(|head| {
            let head = *head;
            self.head = head.next;

            if self.head.is_none() {
                self.tail = ptr::null_mut();
            }
            head.elem
        })
    }
#[cfg(test)]
mod tests {
    use super::List;

    #[test]
    fn basics() {
        let mut list = List::new();
        assert_eq!(list.pop(), None);

        list.push(1);
        list.push(2);
        list.push(3);

        assert_eq!(list.pop(), Some(1));
        assert_eq!(list.pop(), Some(2));
        list.push(4);
        assert_eq!(list.pop(), Some(3));
        assert_eq!(list.pop(), Some(4));
        assert_eq!(list.pop(), None);
    }
}
use std::ptr;
pub struct List<T> {
    head: Link<T>,
    tail: *mut Node<T>,
}

type Link<T> = Option<Box<Node<T>>>;

struct Node<T> {
    elem: T,
    next: Link<T>,
}

impl<T> List<T> {
    pub fn new() -> Self {
        List { head: None, tail: ptr::null_mut() }
    }

    pub fn push(&mut self, elem: T)     {
        let mut new_tail = Box::new(Node {
            elem: elem,
            next: None,
        });

        let raw_tail: *mut _ = &mut *new_tail;

        if !self.tail.is_null() {
            unsafe {
                (*self.tail).next = Some(new_tail);
            }
        } else {
            self.head = Some(new_tail);
        }

        self.tail = raw_tail;
    }

    pub fn pop(&mut self) -> Option<T> {
        self.head.take().map(|head| {
            let head = *head;
            self.head = head.next;

            if self.head.is_none() {
                self.tail = ptr::null_mut();
            }
            head.elem
        })
    }
}

#[cfg(test)]
mod tests {
    use super::List;

    #[test]
    fn basics() {
        let mut list = List::new();
        assert_eq!(list.pop(), None);

        list.push(1);
        list.push(2);
        list.push(3);

        assert_eq!(list.pop(), Some(1));
        assert_eq!(list.pop(), Some(2));
        list.push(4);
        assert_eq!(list.pop(), Some(3));
        assert_eq!(list.pop(), Some(4));
        assert_eq!(list.pop(), None);
    }
}
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