Add Queue and Stack

tools/iterables.ts

@@ -0,0 +1,88 @@
+/**
+ * Data structure allowing for the insertion and removal of
+ * elements in a FIFO manner in `O(1)` time.
+ * @author MindfulMinun
+ * @since 2022-10-22
+ */
+export class Queue<T> implements Iterable<T> {
+    #elements: Record<number, T>
+    #head: number
+    #tail: number
+
+    constructor(initials: Iterable<T>) {
+        this.#elements = {}
+        this.#head = 0
+        this.#tail = 0
+        if (!initials) return
+        for (const el of initials) this.enqueue(el)
+    }
+
+    /** Add an element to the queue */
+    enqueue(element: T): void {
+        this.#elements[this.#tail++] = element
+    }
+
+    /** Remove an element from the queue and return it. */
+    dequeue(): T | undefined {
+        if (this.length === 0) return undefined
+        const el = this.#elements[this.#head]
+        delete this.#elements[this.#head++]
+        return el
+    }
+
+    peek(): T | undefined {
+        if (this.length === 0) return undefined
+        return this.#elements[this.#head]
+    }
+
+    /** The number of elements remaining in the queue */
+    get length() { return this.#tail - this.#head }
+
+    *[Symbol.iterator]() {
+        while (this.length !== 0) yield this.dequeue()!
+    }
+}
+
+
+/**
+ * Data structure allowing for the insertion and removal of
+ * elements in a LIFO manner in `O(1)` time.
+ * @author MindfulMinun
+ * @since 2022-10-22
+ */
+export class Stack<T> implements Iterable<T> {
+    #elements: Record<number, T>
+    #top: number
+
+    constructor(initials?: Iterable<T>) {
+        this.#elements = {}
+        this.#top = 0
+        if (!initials) return
+        for (const el of initials) this.push(el)
+    }
+
+    /** Add an element to the stack */
+    push(element: T): void {
+        this.#elements[this.#top++] = element
+    }
+
+    /** Remove an element from the stack and return it. */
+    pop(): T | undefined {
+        if (this.length === 0) return undefined
+        const el = this.#elements[--this.#top]
+        delete this.#elements[this.#top]
+        return el
+    }
+
+    peek(): T | undefined {
+        if (this.length === 0) return undefined
+        return this.#elements[this.#top - 1]
+    }
+
+    /** The number of elements remaining in the stack */
+    get length() { return this.#top }
+
+    *[Symbol.iterator]() {
+        while (this.length !== 0) yield this.pop()!
+    }
+}