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const debug = @import("debug.zig");
const assert = debug.assert;
const mem = @import("mem.zig");
const Allocator = mem.Allocator;
/// Generic doubly linked list.
pub fn LinkedList(comptime T: type) -> type {
struct {
const Self = this;
/// Node inside the linked list wrapping the actual data.
pub const Node = struct {
prev: ?&Node,
next: ?&Node,
data: T,
pub fn init(data: &const T) -> Node {
Node {
.prev = null,
.next = null,
.data = *data,
}
}
};
first: ?&Node,
last: ?&Node,
len: usize,
/// Initialize a linked list.
///
/// Returns:
/// An empty linked list.
pub fn init() -> Self {
Self {
.first = null,
.last = null,
.len = 0,
}
}
/// Insert a new node after an existing one.
///
/// Arguments:
/// node: Pointer to a node in the list.
/// new_node: Pointer to the new node to insert.
pub fn insertAfter(list: &Self, node: &Node, new_node: &Node) {
new_node.prev = node;
if (node.next) |next_node| {
// Intermediate node.
new_node.next = next_node;
next_node.prev = new_node;
} else {
// Last element of the list.
new_node.next = null;
list.last = new_node;
}
node.next = new_node;
list.len += 1;
}
/// Insert a new node before an existing one.
///
/// Arguments:
/// node: Pointer to a node in the list.
/// new_node: Pointer to the new node to insert.
pub fn insertBefore(list: &Self, node: &Node, new_node: &Node) {
new_node.next = node;
if (node.prev) |prev_node| {
// Intermediate node.
new_node.prev = prev_node;
prev_node.next = new_node;
} else {
// First element of the list.
new_node.prev = null;
list.first = new_node;
}
node.prev = new_node;
list.len += 1;
}
/// Insert a new node at the end of the list.
///
/// Arguments:
/// new_node: Pointer to the new node to insert.
pub fn append(list: &Self, new_node: &Node) {
if (list.last) |last| {
// Insert after last.
list.insertAfter(last, new_node);
} else {
// Empty list.
list.prepend(new_node);
}
}
/// Insert a new node at the beginning of the list.
///
/// Arguments:
/// new_node: Pointer to the new node to insert.
pub fn prepend(list: &Self, new_node: &Node) {
if (list.first) |first| {
// Insert before first.
list.insertBefore(first, new_node);
} else {
// Empty list.
list.first = new_node;
list.last = new_node;
new_node.prev = null;
new_node.next = null;
list.len = 1;
}
}
/// Remove a node from the list.
///
/// Arguments:
/// node: Pointer to the node to be removed.
pub fn remove(list: &Self, node: &Node) {
if (node.prev) |prev_node| {
// Intermediate node.
prev_node.next = node.next;
} else {
// First element of the list.
list.first = node.next;
}
if (node.next) |next_node| {
// Intermediate node.
next_node.prev = node.prev;
} else {
// Last element of the list.
list.last = node.prev;
}
list.len -= 1;
}
/// Remove and return the last node in the list.
///
/// Returns:
/// A pointer to the last node in the list.
pub fn pop(list: &Self) -> ?&Node {
const last = list.last ?? return null;
list.remove(last);
return last;
}
/// Remove and return the first node in the list.
///
/// Returns:
/// A pointer to the first node in the list.
pub fn popFirst(list: &Self) -> ?&Node {
const first = list.first ?? return null;
list.remove(first);
return first;
}
/// Allocate a new node.
///
/// Arguments:
/// allocator: Dynamic memory allocator.
///
/// Returns:
/// A pointer to the new node.
pub fn allocateNode(list: &Self, allocator: &Allocator) -> %&Node {
allocator.create(Node)
}
/// Deallocate a node.
///
/// Arguments:
/// node: Pointer to the node to deallocate.
/// allocator: Dynamic memory allocator.
pub fn destroyNode(list: &Self, node: &Node, allocator: &Allocator) {
allocator.destroy(node);
}
/// Allocate and initialize a node and its data.
///
/// Arguments:
/// data: The data to put inside the node.
/// allocator: Dynamic memory allocator.
///
/// Returns:
/// A pointer to the new node.
pub fn createNode(list: &Self, data: &const T, allocator: &Allocator) -> %&Node {
var node = %return list.allocateNode(allocator);
*node = Node.init(data);
return node;
}
}
}
test "basic linked list test" {
const allocator = debug.global_allocator;
var list = LinkedList(u32).init();
var one = %%list.createNode(1, allocator);
var two = %%list.createNode(2, allocator);
var three = %%list.createNode(3, allocator);
var four = %%list.createNode(4, allocator);
var five = %%list.createNode(5, allocator);
defer {
list.destroyNode(one, allocator);
list.destroyNode(two, allocator);
list.destroyNode(three, allocator);
list.destroyNode(four, allocator);
list.destroyNode(five, allocator);
}
list.append(two); // {2}
list.append(five); // {2, 5}
list.prepend(one); // {1, 2, 5}
list.insertBefore(five, four); // {1, 2, 4, 5}
list.insertAfter(two, three); // {1, 2, 3, 4, 5}
// Traverse forwards.
{
var it = list.first;
var index: u32 = 1;
while (it) |node| : (it = node.next) {
assert(node.data == index);
index += 1;
}
}
// Traverse backwards.
{
var it = list.last;
var index: u32 = 1;
while (it) |node| : (it = node.prev) {
assert(node.data == (6 - index));
index += 1;
}
}
var first = list.popFirst(); // {2, 3, 4, 5}
var last = list.pop(); // {2, 3, 4}
list.remove(three); // {2, 4}
assert ((??list.first).data == 2);
assert ((??list.last ).data == 4);
assert (list.len == 2);
}
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