Add Double Singly-Linked list example

This commit is contained in:
Timothy Warren 2019-03-13 12:34:22 -04:00
parent 0e92a87719
commit 07d33735c6
2 changed files with 142 additions and 0 deletions

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@ -3,3 +3,5 @@ pub mod second;
pub mod third; pub mod third;
pub mod fourth; pub mod fourth;
pub mod fifth; pub mod fifth;
pub mod silly1;

140
src/silly1.rs Normal file
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@ -0,0 +1,140 @@
//! # The Double Singly-Linked List
#[derive(Debug)]
pub struct List<T> {
left: Stack<T>,
right: Stack<T>,
}
#[derive(Debug)]
pub struct Stack<T> {
head: Link<T>,
}
type Link<T> = Option<Box<Node<T>>>;
#[derive(Debug)]
struct Node<T> {
elem: T,
next: Link<T>,
}
impl<T> Stack<T> {
pub fn new() -> Self {
Stack { head: None }
}
pub fn push(&mut self, elem: T) {
let new_node = Box::new(Node {
elem,
next: None,
});
self.push_node(new_node);
}
fn push_node(&mut self, mut node: Box<Node<T>>) {
node.next = self.head.take();
self.head = Some(node);
}
pub fn pop(&mut self) -> Option<T> {
self.pop_node().map(|node| {
node.elem
})
}
fn pop_node(&mut self) -> Link<T> {
self.head.take().map(|mut node| {
self.head = node.next.take();
node
})
}
pub fn peek(&self) -> Option<&T> {
self.head.as_ref().map(|node| {
&node.elem
})
}
pub fn peek_mut(&mut self) -> Option<&mut T> {
self.head.as_mut().map(|node| {
&mut node.elem
})
}
}
impl<T> Drop for Stack<T> {
fn drop(&mut self) {
let mut cur_link = self.head.take();
while let Some(mut boxed_node) = cur_link {
cur_link = boxed_node.next.take();
}
}
}
impl<T> List<T> {
pub fn new() -> Self {
List{
left: Stack::new(),
right: Stack::new(),
}
}
pub fn push_left(&mut self, elem: T) { self.left.push(elem) }
pub fn push_right(&mut self, elem: T) { self.right.push(elem) }
pub fn pop_left(&mut self) -> Option<T> { self.left.pop() }
pub fn pop_right(&mut self) -> Option<T> { self.right.pop() }
pub fn peek_left(&self) -> Option<&T> { self.left.peek() }
pub fn peek_right(&self) -> Option<&T> { self.right.peek() }
pub fn peek_left_mut(&mut self) -> Option<&mut T> { self.left.peek_mut() }
pub fn peek_right_mut(&mut self) -> Option<&mut T> { self.right.peek_mut() }
pub fn go_left(&mut self) -> bool {
self.left.pop_node().map(|node| {
self.right.push_node(node);
}).is_some()
}
pub fn go_right(&mut self) -> bool {
self.right.pop_node().map(|node| {
self.left.push_node(node);
}).is_some()
}
}
#[cfg(test)]
mod test {
use super::List;
#[test]
fn walk_aboot() {
let mut list = List::new(); // [_]
list.push_left(0); // [0,_]
list.push_right(1); // [0, _, 1]
assert_eq!(list.peek_left(), Some(&0));
assert_eq!(list.peek_right(), Some(&1));
list.push_left(2); // [0, 2, _, 1]
list.push_left(3); // [0, 2, 3, _, 1]
list.push_right(4); // [0, 2, 3, _, 4, 1]
while list.go_left() {} // [_, 0, 2, 3, 4, 1]
assert_eq!(list.pop_left(), None);
assert_eq!(list.peek_right(), Some(&0));
assert_eq!(list.pop_right(), Some(0)); // [_, 2, 3, 4, 1]
assert_eq!(list.pop_right(), Some(2)); // [_, 3, 4, 1]
list.push_left(5); // [5, _, 3, 4, 1]
assert_eq!(list.pop_right(), Some(3)); // [5, _, 4, 1]
assert_eq!(list.pop_left(), Some(5)); // [_, 4, 1]
assert_eq!(list.pop_right(), Some(4)); // [_, 1]
assert_eq!(list.pop_right(), Some(1)); // [_]
assert_eq!(list.pop_right(), None);
assert_eq!(list.pop_left(), None);
}
}