347 lines
10 KiB
Zig
347 lines
10 KiB
Zig
const std = @import("std.zig");
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const debug = std.debug;
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const assert = debug.assert;
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const testing = std.testing;
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const mem = std.mem;
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const Allocator = mem.Allocator;
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/// Generic doubly linked list.
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pub fn LinkedList(comptime T: type) type {
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return struct {
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const Self = @This();
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/// Node inside the linked list wrapping the actual data.
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pub const Node = struct {
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prev: ?*Node,
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next: ?*Node,
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data: T,
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pub fn init(data: T) Node {
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return Node{
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.prev = null,
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.next = null,
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.data = data,
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};
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}
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};
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first: ?*Node,
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last: ?*Node,
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len: usize,
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/// Initialize a linked list.
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///
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/// Returns:
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/// An empty linked list.
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pub fn init() Self {
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return Self{
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.first = null,
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.last = null,
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.len = 0,
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};
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}
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/// Insert a new node after an existing one.
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///
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/// Arguments:
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/// node: Pointer to a node in the list.
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/// new_node: Pointer to the new node to insert.
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pub fn insertAfter(list: *Self, node: *Node, new_node: *Node) void {
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new_node.prev = node;
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if (node.next) |next_node| {
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// Intermediate node.
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new_node.next = next_node;
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next_node.prev = new_node;
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} else {
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// Last element of the list.
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new_node.next = null;
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list.last = new_node;
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}
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node.next = new_node;
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list.len += 1;
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}
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/// Insert a new node before an existing one.
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///
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/// Arguments:
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/// node: Pointer to a node in the list.
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/// new_node: Pointer to the new node to insert.
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pub fn insertBefore(list: *Self, node: *Node, new_node: *Node) void {
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new_node.next = node;
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if (node.prev) |prev_node| {
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// Intermediate node.
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new_node.prev = prev_node;
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prev_node.next = new_node;
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} else {
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// First element of the list.
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new_node.prev = null;
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list.first = new_node;
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}
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node.prev = new_node;
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list.len += 1;
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}
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/// Concatenate list2 onto the end of list1, removing all entries from the former.
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///
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/// Arguments:
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/// list1: the list to concatenate onto
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/// list2: the list to be concatenated
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pub fn concatByMoving(list1: *Self, list2: *Self) void {
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const l2_first = list2.first orelse return;
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if (list1.last) |l1_last| {
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l1_last.next = list2.first;
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l2_first.prev = list1.last;
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list1.len += list2.len;
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} else {
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// list1 was empty
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list1.first = list2.first;
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list1.len = list2.len;
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}
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list1.last = list2.last;
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list2.first = null;
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list2.last = null;
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list2.len = 0;
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}
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/// Insert a new node at the end of the list.
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///
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/// Arguments:
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/// new_node: Pointer to the new node to insert.
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pub fn append(list: *Self, new_node: *Node) void {
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if (list.last) |last| {
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// Insert after last.
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list.insertAfter(last, new_node);
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} else {
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// Empty list.
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list.prepend(new_node);
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}
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}
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/// Insert a new node at the beginning of the list.
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///
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/// Arguments:
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/// new_node: Pointer to the new node to insert.
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pub fn prepend(list: *Self, new_node: *Node) void {
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if (list.first) |first| {
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// Insert before first.
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list.insertBefore(first, new_node);
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} else {
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// Empty list.
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list.first = new_node;
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list.last = new_node;
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new_node.prev = null;
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new_node.next = null;
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list.len = 1;
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}
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}
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/// Remove a node from the list.
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///
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/// Arguments:
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/// node: Pointer to the node to be removed.
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pub fn remove(list: *Self, node: *Node) void {
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if (node.prev) |prev_node| {
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// Intermediate node.
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prev_node.next = node.next;
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} else {
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// First element of the list.
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list.first = node.next;
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}
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if (node.next) |next_node| {
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// Intermediate node.
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next_node.prev = node.prev;
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} else {
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// Last element of the list.
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list.last = node.prev;
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}
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list.len -= 1;
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assert(list.len == 0 or (list.first != null and list.last != null));
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}
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/// Remove and return the last node in the list.
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///
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/// Returns:
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/// A pointer to the last node in the list.
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pub fn pop(list: *Self) ?*Node {
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const last = list.last orelse return null;
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list.remove(last);
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return last;
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}
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/// Remove and return the first node in the list.
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///
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/// Returns:
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/// A pointer to the first node in the list.
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pub fn popFirst(list: *Self) ?*Node {
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const first = list.first orelse return null;
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list.remove(first);
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return first;
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}
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/// Allocate a new node.
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///
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/// Arguments:
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/// allocator: Dynamic memory allocator.
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///
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/// Returns:
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/// A pointer to the new node.
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pub fn allocateNode(list: *Self, allocator: *Allocator) !*Node {
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return allocator.create(Node);
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}
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/// Deallocate a node.
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///
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/// Arguments:
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/// node: Pointer to the node to deallocate.
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/// allocator: Dynamic memory allocator.
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pub fn destroyNode(list: *Self, node: *Node, allocator: *Allocator) void {
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allocator.destroy(node);
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}
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/// Allocate and initialize a node and its data.
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///
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/// Arguments:
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/// data: The data to put inside the node.
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/// allocator: Dynamic memory allocator.
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///
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/// Returns:
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/// A pointer to the new node.
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pub fn createNode(list: *Self, data: T, allocator: *Allocator) !*Node {
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var node = try list.allocateNode(allocator);
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node.* = Node.init(data);
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return node;
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}
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};
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}
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test "basic linked list test" {
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const allocator = debug.global_allocator;
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var list = LinkedList(u32).init();
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var one = try list.createNode(1, allocator);
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var two = try list.createNode(2, allocator);
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var three = try list.createNode(3, allocator);
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var four = try list.createNode(4, allocator);
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var five = try list.createNode(5, allocator);
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defer {
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list.destroyNode(one, allocator);
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list.destroyNode(two, allocator);
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list.destroyNode(three, allocator);
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list.destroyNode(four, allocator);
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list.destroyNode(five, allocator);
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}
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list.append(two); // {2}
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list.append(five); // {2, 5}
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list.prepend(one); // {1, 2, 5}
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list.insertBefore(five, four); // {1, 2, 4, 5}
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list.insertAfter(two, three); // {1, 2, 3, 4, 5}
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// Traverse forwards.
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{
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var it = list.first;
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var index: u32 = 1;
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while (it) |node| : (it = node.next) {
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testing.expect(node.data == index);
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index += 1;
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}
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}
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// Traverse backwards.
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{
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var it = list.last;
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var index: u32 = 1;
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while (it) |node| : (it = node.prev) {
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testing.expect(node.data == (6 - index));
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index += 1;
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}
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}
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var first = list.popFirst(); // {2, 3, 4, 5}
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var last = list.pop(); // {2, 3, 4}
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list.remove(three); // {2, 4}
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testing.expect(list.first.?.data == 2);
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testing.expect(list.last.?.data == 4);
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testing.expect(list.len == 2);
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}
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test "linked list concatenation" {
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const allocator = debug.global_allocator;
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var list1 = LinkedList(u32).init();
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var list2 = LinkedList(u32).init();
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var one = try list1.createNode(1, allocator);
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defer list1.destroyNode(one, allocator);
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var two = try list1.createNode(2, allocator);
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defer list1.destroyNode(two, allocator);
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var three = try list1.createNode(3, allocator);
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defer list1.destroyNode(three, allocator);
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var four = try list1.createNode(4, allocator);
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defer list1.destroyNode(four, allocator);
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var five = try list1.createNode(5, allocator);
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defer list1.destroyNode(five, allocator);
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list1.append(one);
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list1.append(two);
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list2.append(three);
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list2.append(four);
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list2.append(five);
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list1.concatByMoving(&list2);
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testing.expect(list1.last == five);
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testing.expect(list1.len == 5);
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testing.expect(list2.first == null);
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testing.expect(list2.last == null);
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testing.expect(list2.len == 0);
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// Traverse forwards.
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{
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var it = list1.first;
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var index: u32 = 1;
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while (it) |node| : (it = node.next) {
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testing.expect(node.data == index);
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index += 1;
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}
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}
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// Traverse backwards.
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{
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var it = list1.last;
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var index: u32 = 1;
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while (it) |node| : (it = node.prev) {
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testing.expect(node.data == (6 - index));
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index += 1;
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}
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}
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// Swap them back, this verifies that concating to an empty list works.
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list2.concatByMoving(&list1);
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// Traverse forwards.
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{
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var it = list2.first;
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var index: u32 = 1;
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while (it) |node| : (it = node.next) {
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testing.expect(node.data == index);
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index += 1;
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}
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}
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// Traverse backwards.
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{
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var it = list2.last;
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var index: u32 = 1;
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while (it) |node| : (it = node.prev) {
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testing.expect(node.data == (6 - index));
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index += 1;
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}
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}
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}
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