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Loïc Grégoire
2026-10-07 18:03:06 -04:00
parent 6cd9117a05
commit 619c373d47
78 changed files with 1676 additions and 1118 deletions
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src/rtl/rbtree.zig
+42 -32
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@@ -1,5 +1,6 @@
//! Red-Black Tree implementation mostly based on pseudocode from CLRS.
//! Refer to the book for details on the algorithms and properties of red-black trees.
//! Refer to the book for details on the algorithms and properties of red-black
//! trees.
const bst = @import("bst.zig");
const std = @import("std");
@@ -7,22 +8,24 @@ const black: u2 = 0;
const red: u2 = 1;
fn get_color(node: *bst.Node) u2 {
return node.parent.get_tag();
return node.parent.tag();
}
fn set_color(node: *bst.Node, color: u2) void {
node.parent.set_tag(color);
}
pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order) type {
pub fn RBTree(
comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order,
) type {
return struct {
tree: bst.BST(cmp),
const Self = @This();
const Tree = @This();
fn rotate_right(self: *Self, node: *bst.Node) void {
fn rotate_right(self: *Tree, node: *bst.Node) void {
var y = node.left;
const parent = node.parent.get_ptr();
const parent = node.parent.ptr();
node.left = y.right;
@@ -44,9 +47,9 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
node.parent.set_ptr(y);
}
fn rotate_left(self: *Self, node: *bst.Node) void {
fn rotate_left(self: *Tree, node: *bst.Node) void {
var y = node.right;
const parent = node.parent.get_ptr();
const parent = node.parent.ptr();
node.right = y.left;
@@ -68,16 +71,19 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
node.parent.set_ptr(y);
}
pub fn init() Self {
return Self{
pub fn init() Tree {
return Tree{
.tree = bst.BST(cmp).init(),
};
}
/// Insert the node `elem` into the tree.
pub fn insert(self: *Self, elem: *bst.Node) !void {
pub fn insert(self: *Tree, elem: *bst.Node) !void {
if (self.tree.is_empty()) {
self.tree.insert(elem) catch unreachable;
self.tree.insert(elem) catch {
// This can't happen as the tree is empty.
unreachable;
};
set_color(elem, black);
return;
}
@@ -90,11 +96,11 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
set_color(elem, red);
var node = elem;
var parent = node.parent.get_ptr();
var parent = node.parent.ptr();
// The tree might be unbalanced, rebalance it.
while (get_color(parent) == red) {
var grandparent = parent.parent.get_ptr();
var grandparent = parent.parent.ptr();
// The parent of the node is a left child
if (parent == grandparent.left) {
@@ -108,19 +114,19 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
set_color(uncle, black);
set_color(grandparent, red);
node = grandparent;
parent = node.parent.get_ptr();
parent = node.parent.ptr();
} else {
// Otherwise, if the node is a right child, rotate left
// to make it a left child.
if (node == parent.right) {
node = parent;
self.rotate_left(node);
parent = node.parent.get_ptr();
grandparent = parent.parent.get_ptr();
parent = node.parent.ptr();
grandparent = parent.parent.ptr();
}
// Then, recolor the parent and grandparent and rotate right
// to maintain the properties of the red-black tree.
// Then, recolor the parent and grandparent and rotate
// right to maintain the invariants.
set_color(parent, black);
set_color(grandparent, red);
self.rotate_right(grandparent);
@@ -134,13 +140,13 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
set_color(uncle, black);
set_color(grandparent, red);
node = grandparent;
parent = node.parent.get_ptr();
parent = node.parent.ptr();
} else {
if (node == parent.left) {
node = parent;
self.rotate_right(node);
parent = node.parent.get_ptr();
grandparent = parent.parent.get_ptr();
parent = node.parent.ptr();
grandparent = parent.parent.ptr();
}
set_color(parent, black);
@@ -148,7 +154,7 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
self.rotate_left(grandparent);
}
parent = node.parent.get_ptr();
parent = node.parent.ptr();
}
}
@@ -156,7 +162,7 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
}
/// Delete the node `elem` from the tree.
pub fn delete(self: *Self, elem: *bst.Node) void {
pub fn delete(self: *Tree, elem: *bst.Node) void {
var node = elem;
var child = &bst.nil;
var orig_color = get_color(node);
@@ -175,7 +181,7 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
orig_color = get_color(node);
child = node.right;
if (node.parent.get_ptr() == elem) {
if (node.parent.ptr() == elem) {
child.parent.set_ptr(node);
} else {
self.tree.transplant(node, node.right);
@@ -198,7 +204,7 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
// Fix the tree
while (node != self.tree.root and get_color(node) == black) {
var parent = node.parent.get_ptr();
var parent = node.parent.ptr();
if (node == parent.left) {
var sibling = parent.right;
@@ -208,11 +214,13 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
set_color(parent, red);
self.rotate_left(parent);
parent = node.parent.get_ptr();
parent = node.parent.ptr();
sibling = parent.right;
}
if (get_color(sibling.left) == black and get_color(sibling.right) == black) {
if (get_color(sibling.left) == black and
get_color(sibling.right) == black)
{
set_color(sibling, red);
node = parent;
} else {
@@ -220,7 +228,7 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
set_color(sibling.left, black);
set_color(sibling, red);
self.rotate_right(sibling);
parent = node.parent.get_ptr();
parent = node.parent.ptr();
sibling = parent.right;
}
@@ -238,11 +246,13 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
set_color(parent, red);
self.rotate_right(parent);
parent = node.parent.get_ptr();
parent = node.parent.ptr();
sibling = parent.left;
}
if (get_color(sibling.left) == black and get_color(sibling.right) == black) {
if (get_color(sibling.left) == black and
get_color(sibling.right) == black)
{
set_color(sibling, red);
node = parent;
} else {
@@ -250,7 +260,7 @@ pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order
set_color(sibling.right, black);
set_color(sibling, red);
self.rotate_left(sibling);
parent = node.parent.get_ptr();
parent = node.parent.ptr();
sibling = parent.left;
}