29:null 2a:["$","title",null,{"children":"Linear Data Structures | Jo Wood | Observable"}] 2f:T4b3,digraph StackOps { rankdir=TB; graph [ranksep=0]; // Vertical spacing fontname="Courier"; node [fontname="monospace", shape=box, width=0.7, height=0.3, fontsize=12]; edge [fontname="monospace",fontsize=10, arrowhead=empty]; // Stack 1 cat1 [label="cat", style=filled, fillcolor="pink"]; bat1 [label="bat"]; ant1 [label="ant"]; cat1 -> bat1 [dir=none]; bat1 -> ant1 [dir=none]; // Stack 2 after pop() dummy [shape=point, width=0, height=0, style=invis]; // invisible node so it still has three rows bat2 [label="bat", style=filled, fillcolor="pink"]; ant2 [label="ant"]; dummy -> bat2 [dir=none, style=invis]; bat2 -> ant2 [dir=none]; // Stack 3 after push() dog3 [label="dog", style=filled, fillcolor="pink"]; bat3 [label="bat"]; ant3 [label="ant"]; dog3 -> bat3 [dir=none]; bat3 -> ant3 [dir=none]; // Force each row to be on the same horizontal rank { rank=same; cat1; dummy; dog3; } { rank=same; bat1; bat2; bat3; } { rank=same; ant1; ant2; ant3; } // Operations as labelled edges cat1 -> bat2 [style=dashed, label=" pop() ", constraint=false]; bat2 -> dog3 [style=dashed, label=" push(dog) ", constraint=false]; }30:T70d,

Stack

Last-in-first-out (LIFO) structure. Insertion and removal are both ${tex`O(1)`} operations.

`constructor(xs: Array<any>)`

Creates a new Stack from an array of values xs, with the first item at the bottom and the last at the top.

`size(): number`

Returns the number of items in the stack.

`isEmpty(): boolean`

Returns true if the stack is empty; otherwise false.

`peek(): any`

Returns the top item of the stack without removing it.
Throws: Error if the stack is empty.

`toArray(): Array<any>`

Returns an array of the stack's values in bottom-to-top order (first = bottom, last = top).

`push(x: any): Stack`

Adds x to the top of the stack. Returns this stack to support method chaining.

`pop(): any`

Removes and returns the top item from the stack.
Throws: Error if the stack is empty.

`clear(): Stack`

Removes all items from the stack. Returns this stack to support method chaining.

31:T71f,

Queue

First-in-first-out (FIFO) structure. Insertion and removal have ${tex`O(1)`} amortised time complexity.

`constructor(xs: Array<any>)`

Creates a new Queue from an array of values xs, where the first element will be dequeued first.

`size(): number`

Returns the number of items in the queue.

`isEmpty(): boolean`

Returns true if the queue is empty; otherwise false.

`peek(): any`

Returns the next item that would be dequeued without removing it.
Throws: Error if the queue is empty.

`toArray(): Array<any>`

Returns an array of the queue's values in FIFO order (front to back).

`enqueue(x: any): Queue`

Adds x to the back of the queue. Returns this queue to support method chaining.

`dequeue(): any`

Removes and returns the item at the front of the queue.
Throws: Error if the queue is empty.

`clear(): Queue`

Removes all items from the queue. Returns this queue to support method chaining.

32:T55b,digraph DequeOps { rankdir=TB; graph [ranksep=0]; // Vertical spacing nodesep=0; // Horizontal spacing node [shape=box, width=0.7, height=0.3, fontname="monospace", fontsize=12]; edge [fontname="monospace",fontsize=10,arrowhead=empty]; r0c0 [label="ant", style=filled, fillcolor="pink"]; // front r0c1 [label="bat"]; r0c2 [label="cat", style=filled, fillcolor="lightblue"]; // back r1c0 [label="bat", style=filled, fillcolor="pink"]; r1c1 [label="cat", style=filled, fillcolor="lightblue"]; r2c0 [label="dog", style=filled, fillcolor="pink"]; r2c1 [label="bat"]; r2c2 [label="cat", style=filled, fillcolor="lightblue"]; r3c0 [label="dog", style=filled, fillcolor="pink"]; r3c1 [label="bat", style=filled, fillcolor="lightblue"]; r4c0 [label="dog", style=filled, fillcolor="pink"]; r4c1 [label="bat"]; r4c2 [label="eel", style=filled, fillcolor="lightblue"]; // Force boxes into rows { rank=same; r0c0; r0c1; r0c2; } { rank=same; r1c0; r1c1; } { rank=same; r2c0; r2c1; r2c2; } { rank=same; r3c0; r3c1; } { rank=same; r4c0; r4c1; r4c2; } // Operations r0c0 -> r1c0 [style=dashed, label=" dequeueFront()"]; r1c0 -> r2c0 [style=dashed, label=" enqueueFront(dog)"]; r2c0 -> r3c0 [style=dashed, label=" dequeueBack()"]; r3c0 -> r4c0 [style=dashed, label=" enqueueBack(eel)"]; }33:Tbd9,

Deque

Double-ended queue supporting both LIFO (stack) and FIFO (queue) behaviour. Can optionally have a fixed capacity making this a circular buffer (enqueuing beyond the capacity replaces existing values). Insertion and removal at both the front and back have ${tex`O(1)`} time complexity.

`constructor(xs: Array<any>, capacity?: number)`

Creates a new Deque from an array of values xs, with the first element at the front and the last at the back. If capacity is provided, the deque behaves as a bounded circular buffer, automatically discarding elements when full.
Throws: RangeError if capacity is neither a positive integer nor Infinity.

`size(): number`

Returns the number of items in the deque.

`isEmpty(): boolean`

Returns true if the deque is empty; otherwise false.

`peekFront(): any`

Returns the item at the front of the deque without removing it.
Throws: Error if the deque is empty.

`peekBack(): any`

Returns the item at the back of the deque without removing it.
Throws: Error if the deque is empty.

`toArray(): Array<any>`

Returns an array of the deque’s values in front-to-back order.

`enqueueFront(x: any): Deque`

Adds x to the front of the deque. Returns this deque to support method chaining.

`enqueueBack(x: any): Deque`

Adds x to the back of the deque. Returns this deque to support method chaining.

`dequeueFront(): any`

Removes and returns the item from the front of the deque.
Throws: Error if the deque is empty.

`dequeueBack(): any`

Removes and returns the item from the back of the deque.
Throws: Error if the deque is empty.

`clear(): Deque`

Removes all items from the deque. Returns this deque to support method chaining.

34:T9e0,

PriorityQueue

A binary heap-based queue where each item is associated with a numeric priority. The item with the smallest priority value is always dequeued first. Enqueue and dequeue operations both have ${tex`O(\log n)`} time complexity. Bulk initialisation via the constructor is ${tex`O(n)`}.

`constructor(entries: Array<[x: any, priority?: number]>)`

Creates a new PriorityQueue from an array of [x, priority] pairs. If a priority is not provided, it defaults to 0.

`size(): number`

Returns the number of items in the queue.

`isEmpty(): boolean`

Returns true if the queue is empty; otherwise false.

`peek(): any`

Returns the next item that would be dequeued without removing it from the queue.
Throws: Error if the queue is empty.

`peekPriority(): number`

Returns the priority of the next item that would be dequeued.
Throws: Error if the queue is empty.

`toArray(): Array<any>`

Returns an array of the queue's values in ascending priority order.

`enqueue(x: any, priority?: number): PriorityQueue`

Adds x to the queue with the given priority. If omitted, priority defaults to 0. Returns this priority queue to support method chaining.

`dequeue(): any`

Removes and returns the item with the smallest priority value.
Throws: Error if the queue is empty.

`clear(): PriorityQueue`

Removes all items from the queue. Returns this priority queue to support method chaining.

35:T4ef,digraph QueueOps { rankdir=TB; graph [ranksep=0]; // Vertical spacing nodesep=0; // Horizontal spacing node [shape=box, width=1, height=0.3, fontname="monospace", fontsize=12]; edge [fontname="monospace", fontsize=10, arrowhead=empty]; empty [style=invis]; r0c0 [label="ant (20)", style=filled, fillcolor="pink"]; r1c0 [label="bat (10)", style=filled, fillcolor="pink"]; r1c1 [label="ant (20)"]; r2c0 [label="bat (10)", style=filled, fillcolor="pink"]; r2c1 [label="ant (20)"]; r2c2 [label="cat (30)"]; r3c0 [label="bat (10)", style=filled, fillcolor="pink"]; r3c1 [label="dog (15)"]; r3c2 [label="ant (20)"]; r4c0 [label="bat (10)", style=filled, fillcolor="pink"]; r4c1 [label="dog (15)"]; r4c2 [label="ant (20)"]; // Force boxes into rows { rank=same; r1c0; r1c1; } { rank=same; r2c0; r2c1; r2c2; } { rank=same; r3c0; r3c1; r3c2; } { rank=same; r4c0; r4c1; r4c2; } // Operations empty -> r0c0 [style=dashed, label=" insert(ant,20)"]; r0c0 -> r1c0 [style=dashed, label=" insert(bat,10)"]; r1c0 -> r2c0 [style=dashed, label=" insert(cat, 30)"]; r2c0 -> r3c0 [style=dashed, label=" insert(dog, 15)"]; r3c0 -> r4c0 [style=dashed, label=" insert(eel, 25)"]; }36:Tc05,

BoundedPriorityQueue

A bounded priority queue stores up to k elements (its capacity) with the lowest numeric priorities. It supports efficient replacement when a new item has a higher priority (i.e. a smaller number). When full, any new item is only inserted if its priority is lower (more important) than the current maximum. Both insertion and removal are ${tex`O(\log k)`}.

`constructor(capacity: number = Infinity)`

Creates a new BoundedPriorityQueue with the given maximum capacity. A capacity of Infinity creates an unbounded queue.
Throws: RangeError if capacity is neither a positive integer nor Infinity.

`size(): number`

Returns the current number of items in the queue.

`isEmpty(): boolean`

Returns true if the queue is empty; otherwise false.

`peek(): any`

Returns the value with the lowest priority (largest numeric priority value) without removing it.
Throws: Error if the queue is empty.

`peekPriority(): number`

Returns the numeric priority of the lowest priority item (largest numeric priority value).
Throws: Error if the queue is empty.

`dequeue(): any`

Removes and returns the item with the largest numeric priority value (the lowest-priority item currently retained).
Throws: Error if the queue is empty.

`insert(x: any, priority: number): BoundedPriorityQueue`

Inserts a value with the given priority. If the queue is at capacity and the new priority is numerically smaller than its current largest priority, the new item displaces the item with that largest value. Returns the queue to allow method chaining.

`toArray(): Array<any>`

Returns an unordered array of the values currently stored in the queue.

`toSortedArray(): Array<any>`

Returns the values in ascending numeric priority order, from highest to lowest importance.

`clear(): BoundedPriorityQueue`

Removes all items from the queue. Returns the queue to allow method chaining.

37:T5fb,digraph DLL_Ops { rankdir=TB; graph [ranksep=0]; // Vertical spacing nodesep=0.4; // Horizontal spacing node [shape=box, width=0.7, height=0.3, fontname="monospace", fontsize=12]; edge [fontname="monospace",fontsize=10]; r0c0 [label="ant", style=filled, fillcolor="pink"]; r0c1 [label="bat"]; r0c2 [label="cat", style=filled, fillcolor="lightblue"]; r0c0 -> r0c1; r0c1 -> r0c0; r0c1 -> r0c2; r0c2 -> r0c1; r1c0 [label="dog", style=filled, fillcolor="pink"]; r1c1 [label="ant"]; r1c2 [label="bat"]; r1c3 [label="cat", style=filled, fillcolor="lightblue"]; r1c0 -> r1c1; r1c1 -> r1c0; r1c1 -> r1c2; r1c2 -> r1c1; r1c2 -> r1c3; r1c3 -> r1c2; r2c0 [label="dog", style=filled, fillcolor="pink"]; r2c1 [label="ant"]; r2c2 [label="cat", style=filled, fillcolor="lightblue"]; r2c0 -> r2c1; r2c1 -> r2c0; r2c1 -> r2c2; r2c2 -> r2c1; r3c0 [label="dog", style=filled, fillcolor="pink"]; r3c1 [label="eel"]; r3c2 [label="ant"]; r3c3 [label="cat", style=filled, fillcolor="lightblue"]; r3c0 -> r3c1; r3c1 -> r3c0; r3c1 -> r3c2; r3c2 -> r3c1; r3c2 -> r3c3; r3c3 -> r3c2; { rank=same; r0c0; r0c1; r0c2; } { rank=same; r1c0; r1c1; r1c2; r1c3; } { rank=same; r2c0; r2c1; r2c2; } { rank=same; r3c0; r3c1; r3c2; r3c3; } r0c0 -> r1c0 [style=dashed, arrowhead=empty, label=" pushFront(dog)"]; r1c0 -> r2c0 [style=dashed, arrowhead=empty, label=" remove(bat)"]; r2c0 -> r3c0 [style=dashed, arrowhead=empty, label=" insertAfter(dog, eel)"]; }38:T152e,

DoublyLinkedList

A mutable, linear structure with efficient insertion and removal at both ends and in the middle. All operations on known nodes are ${tex`O(1)`}. Searching or accessing by index is ${tex`O(n)`}.

`constructor(xs: Array<any>)`

Creates a new DoublyLinkedList from an array of values xs, with the first element at the front and the last at the back.

`size(): number`

Returns the number of items in the list.

`isEmpty(): boolean`

Returns true if the list is empty; otherwise false.

`peekFront(): any`

Returns the value at the front of the list without removing it.
Throws: Error if the list is empty.

`peekBack(): any`

Returns the value at the back of the list without removing it.
Throws: Error if the list is empty.

`toArray(): Array<any>`

Returns an array of the list's values in front-to-back order.

`pushFront(x: any): DoublyLinkedList`

Adds x to the front of the list. Returns this list to support method chaining.

`pushBack(x: any): DoublyLinkedList`

Adds x to the back of the list. Returns this list to support method chaining.

`popFront(): any`

Removes and returns the value from the front of the list.
Throws: Error if the list is empty.

`popBack(): any`

Removes and returns the value from the back of the list.
Throws: Error if the list is empty.

`clear(): DoublyLinkedList`

Removes all items from the list. Returns this list to support method chaining.

`indexOf(x: any): number`

Returns the index of the first instance of the given value in the list, or -1 if not found.

`find(pred: (x: any) => boolean): object | null`

Returns a reference to the first node whose value satisfies pred, or null if no match is found.

`findLast(pred: (x: any) => boolean): object | null`

Returns a reference to the last node in the list whose value satisfies pred, or null if no match is found.

`insertAt(i: number, x: any): DoublyLinkedList`

Inserts x at position i; the former item at that position and subsequent items have their indices increased by one. Returns this list to support method chaining.
Throws: Error if i is out of bounds.

`insertAfter(node: object, x: any): DoublyLinkedList`

Inserts x immediately after the given node. The node must belong to this list and would normally be obtained from find() or findLast() Returns this list to support method chaining.
Throws: Error if node is null.

`insertBefore(node: object, x: any): DoublyLinkedList`

Inserts x immediately before the given node. The node must belong to this list and would normally be obtained from find() or findLast() Returns this list to support method chaining.
Throws: Error if node is null.

`removeAt(i: number): any`

Removes and returns the value at position i.
Throws: Error if i is out of bounds.

`remove(node: object | null): any | null`

Removes the specified node and returns its value. The node must belong to this list and would normally be obtained from find() or findLast(). Returns null if node is null.

39:[] 2d:{"id":"365dcc743ba73556","slug":"data-structures-linear","title":"Linear Data Structures","thumbnail":"0215af3d92b259ece2f7195733fcd95a04bb8405a1b5577d8eb54a80280af1be","access_level":"public","create_time":"$D2025-07-23T04:31:45.061Z","update_time":"$D2026-09-22T09:18:19.498Z","view_time":null,"first_public_time":"$D2026-09-22T14:23:36.455Z","has_unpublished_edits":null,"fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"9461f58b209074d5","login":"jwolondon","name":"Jo Wood","avatar_url":"https://avatars-next.observableusercontent.com/27f72cecd1ac20853a533421fab228ce5f611cbc0986c1e420f7d3b1eb49ef50","tier":"starter_2024"},"version":793,"publish_version":793,"role":null,"authored":false,"authors":[{"type":"individual","id":"e2432cc13dc447d3","login":"jwolondon","name":"Jo Wood","avatar_url":"https://avatars-next.observableusercontent.com/27f72cecd1ac20853a533421fab228ce5f611cbc0986c1e420f7d3b1eb49ef50","tier":null}],"members":[{"type":"individual","id":"e2432cc13dc447d3","login":"jwolondon","name":"Jo Wood","avatar_url":"https://avatars-next.observableusercontent.com/27f72cecd1ac20853a533421fab228ce5f611cbc0986c1e420f7d3b1eb49ef50","tier":null,"role":"editor"},{"type":"team","id":"9461f58b209074d5","login":"jwolondon","name":"Jo Wood","avatar_url":"https://avatars-next.observableusercontent.com/27f72cecd1ac20853a533421fab228ce5f611cbc0986c1e420f7d3b1eb49ef50","tier":"starter_2024","role":"viewer"}],"comments":[],"custom_thumbnail":true,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":{"id":"cf3a41cde0560514","slug":"data-structures","title":"data structures","owner":{"id":"9461f58b209074d5","login":"jwolondon","name":"Jo Wood"}},"type":"notebook","body":{"title":"Linear Data Structures","cells":[{"id":0,"value":"# Linear Data Structures","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":5,"value":"## 1. Stack","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":69,"value":"A [stack](https://en.wikipedia.org/wiki/Stack_%28abstract_data_type%29) stores a sequence of values in 'last-in-first-out' (LIFO) order. Items are added by enqueuing them at the back of the sequence and removed by dequeuing them from the front. Enqueuing takes ${tex`O(1)`} time (i.e. the time taken to push or pop is fixed, regardless of how many items in the stack), while dequeuing takes ${tex`O(1)`} amortised time (i.e. average time complexity is fixed). The front of the stack, shaded pink below, can be examined with `peek()`.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":174,"value":"For example,\n\n```javascript\nimport { Stack } from \"observable:@jwolondon/adts-and-data-structures\"\n\nconst myStack = new Stack([\"ant\", \"bat\", \"cat\"]);\nmyStack.pop();\nmyStack.push(\"dog\");\n```","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":121,"value":"$2f","pinned":false,"hidden":false,"mode":"dot","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":199,"value":"### API","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":7,"value":"$30","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":11,"value":"## 2. Queue","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":201,"value":"A [queue](https://en.wikipedia.org/wiki/Queue_%28abstract_data_type%29) stores a sequence of values in 'first-in-first-out' (FIFO) order. Items are added by 'enqueuing' to the back of the sequence and removed from the front by 'dequeuing'. Both are ${tex`O(1)`} efficient (i.e. the time taken to enqueue or dequeue is fixed, regardless of how many items in the queue). The front of the queue, shaded pink below, can be examined with `peek()`.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":399,"value":"For example,\n\n```javascript\nimport { Queue } from \"observable:@jwolondon/adts-and-data-structures\"\n\nconst myQueue = new Queue([\"ant\", \"bat\", \"cat\"]);\nmyQueue.dequeue();\nmyQueue.enqueue(\"dog\");\n```","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":348,"value":"digraph QueueOps {\n rankdir=TB;\n graph [ranksep=0]; // Vertical spacing\n nodesep=0; // Horizontal spacing\n\n node [shape=box, width=0.7, height=0.3, fontname=\"monospace\", fontsize=12];\n edge [fontname=\"monospace\",fontsize=10, arrowhead=empty];\n\n r0c0 [label=\"ant\", style=filled, fillcolor=\"pink\"];\n r0c1 [label=\"bat\"];\n r0c2 [label=\"cat\"];\n\n r1c0 [label=\"bat\", style=filled, fillcolor=\"pink\"];\n r1c1 [label=\"cat\"];\n\n r2c0 [label=\"bat\", style=filled, fillcolor=\"pink\"];\n r2c1 [label=\"cat\"];\n r2c2 [label=\"dog\"];\n\n // Force boxes into rows\n { rank=same; r0c0; r0c1; r0c2; }\n { rank=same; r1c0; r1c1; }\n { rank=same; r2c0; r2c1; r2c2; }\n\n // Operations\n r0c0 -> r1c0 [style=dashed, label=\" dequeue()\"];\n r1c0 -> r2c0 [style=dashed, label=\" enqueue('dog')\"];\n}","pinned":false,"hidden":false,"mode":"dot","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":25,"value":"$31","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":27,"value":"## 3. Double-ended queue (deque)","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":446,"value":"A [double-ended queue](https://en.wikipedia.org/wiki/Double-ended_queue) (or _deque_, pronounced 'deck') stores a sequence of values that supports both LIFO (stack) and FIFO (queue) usage. Items can be efficiently enqueued and dequeued from either end of the deque with ${tex`O(1)`} time complexity. In the diagram below, the front of the deque is shaded pink and the back shaded blue.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":33,"value":"For example,\n\n```js\nimport { Deque } from \"observable:@jwolondon/adts-and-data-structures\"\n\nconst myDeque = new Deque([\"ant\", \"bat\", \"cat\"]);\nmyDeque.dequeueFront();\nmyDeque.enqueueFront(\"dog\");\nmyDeque.dequeueBack();\nmyDeque.enqueueBack(\"eel\");\n```","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":464,"value":"$32","pinned":false,"hidden":false,"mode":"dot","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":35,"value":"$33","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":37,"value":"## 4. Priority Queue","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":537,"value":"A [priority queue](https://en.wikipedia.org/wiki/Priority_queue) is similar to a standard queue, except that instead of the sequence of values being determined by the insert order, they are determined by a separate _priority_ number. The lower the number the higher the priority. This allows a sequence to be maintained in some user-driven order. Dequeuing removes, and peeking examines, the item with the smallest numeric priority. Items with equal priority values are dequeued in insertion order.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":39,"value":"For example,\n\n```js\nimport { PriorityQueue } from \"observable:@jwolondon/adts-and-data-structures\"\n\nconst myPriorityQueue = new PriorityQueue([[\"ant\", 20], [\"bat\", 10], [\"cat\", 30]]);\nmyPriorityQueue.dequeue();\nmyPriorityQueue.enqueue(\"dog\", 25);\n```","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":516,"value":"digraph QueueOps {\n rankdir=TB;\n graph [ranksep=0]; // Vertical spacing\n nodesep=0; // Horizontal spacing\n\n node [shape=box, width=1, height=0.3, fontname=\"monospace\", fontsize=12];\n edge [fontname=\"monospace\",fontsize=10,arrowhead=empty,];\n\n r0c0 [label=\"bat (10)\", style=filled, fillcolor=\"pink\"];\n r0c1 [label=\"ant (20)\"];\n r0c2 [label=\"cat (30)\"];\n\n r1c0 [label=\"ant (20)\", style=filled, fillcolor=\"pink\"];\n r1c1 [label=\"cat (30)\"];\n\n r2c0 [label=\"ant (20)\", style=filled, fillcolor=\"pink\"];\n r2c1 [label=\"dog (25)\"];\n r2c2 [label=\"cat (30)\"];\n\n // Force boxes into rows\n { rank=same; r0c0; r0c1; r0c2; }\n { rank=same; r1c0; r1c1; }\n { rank=same; r2c0; r2c1; r2c2; }\n\n // Operations\n r0c0 -> r1c0 [style=dashed, label=\" dequeue()\"];\n r1c0 -> r2c0 [style=dashed, label=\" enqueue(dog, 25)\"];\n}","pinned":false,"hidden":false,"mode":"dot","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":42,"value":"$34","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":44,"value":"## 5. Bounded Priority Queue","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":575,"value":"A bounded priority queue is a specialised priority queue with a fixed _capacity_. When it is full, an item is inserted only if its numeric priority is smaller than the largest numeric priority currently retained. The new item then displaces that least-important item. An equal or larger numeric priority is ignored. Internally, the queue uses a max-heap so that the least-important retained item can be found efficiently.\n\nThis is useful for representing the 'top _k_' items in an ordered list.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":587,"value":"For example, here are some insertions into a `BoundedPriorityQueue` with a capacity of 3:\n\n```javascript\nimport {BoundedPriorityQueue} from \"observable:@jwolondon/adts-and-data-structures\"\n\nconst myBoundedPQ = new BoundedPriorityQueue(3)\n .insert(\"ant\", 20)\n .insert(\"bat\", 10)\n .insert(\"cat\", 30)\n .insert(\"dog\", 15)\n .insert(\"eel\", 25);\n```","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":549,"value":"$35","pinned":false,"hidden":false,"mode":"dot","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":50,"value":"$36","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":52,"value":"## 6. Doubly Linked List","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":700,"value":"A [doubly linked list](https://en.wikipedia.org/wiki/Doubly_linked_list) stores an ordered sequence of values. Each node contains links to its previous and next neighbours, or null at the ends of the list. Insertion or removal at either end, or relative to a known node, takes ${tex`O(1)`} time. Finding a value or locating a node by index takes ${tex`O(n)`} time. The list can be traversed efficiently in either direction.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":54,"value":"For example,\n\n```js\nimport { DoublyLinkedList } from \"observable:@jwolondon/adts-and-data-structures\"\n\nconst myDll = new DoublyLinkedList([\"ant\", \"bat\", \"cat\"]);\nmyDll.pushFront(\"dog\");\nmyDll.remove(myDll.find((x) => x === \"bat\"));\nmyDll.insertAfter(myDll.find((x) => x === \"dog\"), \"eel\");\n```","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":605,"value":"$37","pinned":false,"hidden":false,"mode":"dot","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":56,"value":"$38","pinned":false,"hidden":false,"mode":"html","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":19,"value":"---\n\n## Appendices","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":23,"value":"_For API doc and page styling:_","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":701,"value":"import {defaultStyle} from \"observable:@jwolondon/utilities-cdt-2026\"","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":21,"value":"import {apiStyle} from \"observable:@jwolondon/data-structure-docs\";","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","output":"","database":"$undefined"},{"id":702,"value":"defaultStyle()","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":60,"value":"apiStyle()","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W39","stdlib":"2","titling":"auto"}} 2e:"$2d:body"