commit 57cfa8ad1999fb198dd91734b383a568756a3f0d
Author: Timothy Warren <twarren@nabancard.com>
Date:   Fri Jul 26 16:25:13 2019 -0400

    First commit

diff --git a/package.json b/package.json
new file mode 100644
index 0000000..6c56408
--- /dev/null
+++ b/package.json
@@ -0,0 +1,4 @@
+{
+  "type": "module",
+  "main": "./src/usage.js"
+}
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diff --git a/src/structures/binary-search-tree.js b/src/structures/binary-search-tree.js
new file mode 100644
index 0000000..dc16e87
--- /dev/null
+++ b/src/structures/binary-search-tree.js
@@ -0,0 +1,118 @@
+const root = Symbol("root");
+
+class BinarySearchTreeNode {
+    constructor (value) {
+        this.value = value;
+        this.left = null;
+        this.right = null;
+    }
+}
+
+class BinarySearchTree {
+    constructor () {
+        this[root] = null;
+    }
+
+    add (value) {
+        const node = new BinarySearchTreeNode(value);
+        let current = null;
+
+        // No items in tree
+        if (this[root] === null) {
+            this[root] = node;
+        } else {
+            current = this[root];
+
+            while (true) {
+                if (value < current.value) {
+                    // If there's no left, insert
+                    if (current.left === null) {
+                        current.left = node;
+                        break;
+                    }
+
+                    current = current.left;
+
+                } else if (value > current.value) {
+                    if (current.right === null) {
+                        current.right = node;
+                        break;
+                    }
+
+                    current = current.right;
+                } else {
+                    break;
+                }
+            }
+        }
+    }
+
+    contains (value) {
+        let found = false;
+        let current = this[root];
+
+        while ( ! found && current !== null) {
+            if (value < current.value) {
+                current = current.left;
+            } else if (value > current.value) {
+                current = current.right;
+            } else if (value === current.value) {
+                found = true;
+            }
+        }
+
+        return found;
+    }
+
+    remove (value) {
+
+    }
+
+    size () {
+        let length = 0;
+
+        this.traverse(() => {
+            length++;
+        });
+
+        return length;
+    }
+
+    traverse (process) {
+        const inOrder = (node) => {
+            if ( ! node) {
+                return;
+            }
+
+            // traverse the left subtree
+            if (node.left !== null) {
+                inOrder(node.left);
+            }
+
+            // handle the current node
+            process.call(this, node);
+
+            // traverse the right subtree
+            if (node.right !== null) {
+                inOrder(node.right);
+            }
+        };
+
+        // start with the root
+        inOrder(this[root]);
+    }
+
+    toArray () {
+        let result = [];
+
+        this.traverse((node) => {
+            result.push(node.value);
+        });
+
+        return result;
+    }
+
+    toString () {
+        return this.toArray().toString();
+    }
+}
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diff --git a/src/structures/circular-doubly-linked-list.js b/src/structures/circular-doubly-linked-list.js
new file mode 100644
index 0000000..ee9c369
--- /dev/null
+++ b/src/structures/circular-doubly-linked-list.js
@@ -0,0 +1,131 @@
+const head = Symbol("head");
+const tail = Symbol("tail");
+
+class CircularDoublyLinkedListNode {
+    constructor (data) {
+        this.data = data;
+        this.next = null;
+        this.previous = null;
+    }
+}
+
+export class CircularDoublyLinkedList {
+    constructor () {
+        this[head] = null;
+        this[tail] = null;
+    }
+
+    add (data) {
+        const newNode = new CircularDoublyLinkedListNode(data);
+
+        // Special case: no items in the list
+        if (this[head] === null) {
+            this[head] = newNode;
+            newNode.next = newNode;
+            newNode.previous = newNode;
+        } else {
+            const tail = this[head].previous;
+
+            tail.next = newNode;
+            newNode.previous = tail;
+            newNode.next = this[head];
+            this[head].previous = newNode;
+        }
+    }
+
+    get (index) {
+        if ( ! Number(index) < 0) {
+            return undefined;
+        }
+
+        let current = this[head];
+        let i = 0;
+
+        do {
+            if (i === index) {
+                return current.data;
+            }
+
+            current = current.next;
+            i++;
+        } while ((current !== this[head]) && (i <= index));
+
+        return undefined;
+    }
+
+    remove (index) {
+        if ((this[head] === null) || (index < 0)) {
+            throw new RangeError(`Index ${index} does not exist in the list.`);
+        }
+
+        let current = this[head];
+
+        // Removing the first node
+        if (index === 0) {
+            if (current.next === this[head]) {
+                this[head] = null;
+            } else {
+                const tail = this[head].previous;
+
+                // Set the tail to point to the second item in the list
+                //  and point the new item to the tail
+                tail.next = current.next;
+                current.next.previous = tail;
+
+                this[head] = tail.next;
+            }
+
+            return current.data;
+        }
+
+        let i = 0;
+
+        do {
+            current = current.next;
+            i++;
+        } while ((current !== this[head]) && (i < index));
+
+        if (current !== this[head]) {
+            // skip over the node to remove it
+            current.previous.next = current.next;
+            current.next.previous = current.previous;
+
+            return current.data;
+        }
+
+        throw new RangeError(`Index ${index} does not exist in the list.`);
+    }
+
+    *values () {
+        // list is empty
+        if (this[head] !== null) {
+            // only one node
+            if (this[head].next === this[head]) {
+                yield this[head].data;
+            } else {
+                let current = this[head];
+
+                do {
+                    yield current.data;
+                    current = current.next;
+                } while (current !== this[head]);
+            }
+        }
+    }
+
+    *circularValues () {
+        if (this[head] !== null) {
+            let current = this[head];
+
+            // infinite loop
+            while (true) {
+                yield current.data;
+                current = current.next;
+            }
+        }
+    }
+
+    [Symbol.iterator] () {
+        return this.values();
+    }
+}
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diff --git a/src/structures/doubly-linked-list.js b/src/structures/doubly-linked-list.js
new file mode 100644
index 0000000..2c9aa7c
--- /dev/null
+++ b/src/structures/doubly-linked-list.js
@@ -0,0 +1,117 @@
+const head = Symbol("head");
+const tail = Symbol("tail");
+
+class DoublyLinkedListNode {
+    constructor (data) {
+        this.data = data;
+        this.next = null;
+        this.previous = null;
+    }
+}
+
+export class DoublyLinkedList {
+    constructor () {
+        this[head] = null;
+        this[tail] = null;
+    }
+
+    add (data) {
+        const newNode = new DoublyLinkedListNode(data);
+
+        // special case: no nodes
+        if (this[head] === null) {
+            this[head] = newNode;
+        } else {
+            // link the current tail and new tail
+            this[tail].next = newNode;
+            newNode.previous = this[tail];
+        }
+
+        // re-assign the tail
+        this[tail] = newNode;
+    }
+
+    get (index) {
+        if ( ! Number(index) < 0) {
+            return undefined;
+        }
+
+        let current = this[head];
+        let i = 0;
+
+        while ((current !== null) && (i < index)) {
+            current = current.next;
+            i++;
+        }
+
+        return current !== null
+            ? current.data
+            : undefined;
+    }
+
+    remove (index) {
+        if ((this[head] === null) || (index < 0)) {
+            throw new RangeError(`Index ${index} does not exist in the list.`);
+        }
+
+        // special case: removing the first node
+        if (index === 0) {
+            const data = this[head].data;
+            this[head] = this[head].next;
+
+            // Only one node
+            if (this[head] === null) {
+                this[tail] = null;
+            } else {
+                this[head].previous = null;
+            }
+
+            return data;
+        }
+
+        let current = this[head];
+        let i = 0;
+        while ((current !== null) && (i < index)) {
+            current = current.next;
+            i++;
+        }
+
+        // If node was found remove it
+        if (current !== null) {
+            current.previous.next = current.next;
+
+            // last node
+            if (this[tail] === current) {
+                this[tail] = current.previous;
+            } else {
+                current.next.previous = current.previous;
+            }
+
+            return current.data;
+        }
+
+        throw new RangeError(`Index ${index} does not exist in the list.`);
+    }
+
+    *values () {
+        let current = this[head];
+
+        while (current !== null) {
+            yield current.data;
+            current = current.next;
+        }
+    }
+
+    *reverse () {
+        let current = this[tail];
+
+        while (current !== null) {
+            yield current.data;
+            current = current.previous;
+        }
+    }
+
+    [Symbol.iterator] () {
+        return this.values();
+    }
+}
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diff --git a/src/structures/index.js b/src/structures/index.js
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--- /dev/null
+++ b/src/structures/index.js
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+import { CircularDoublyLinkedList } from "./circular-doubly-linked-list";
+import { DoublyLinkedList } from "./doubly-linked-list";
+import { LinkedList } from "./linked-list";
+
+export {
+    CircularDoublyLinkedList,
+    DoublyLinkedList,
+    LinkedList,
+};
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diff --git a/src/structures/linked-list.js b/src/structures/linked-list.js
new file mode 100644
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+++ b/src/structures/linked-list.js
@@ -0,0 +1,103 @@
+const head = Symbol("head");
+
+class LinkedListNode {
+    constructor (data) {
+        this.data = data;
+        this.next = null;
+    }
+}
+
+export class LinkedList {
+    constructor () {
+        this[head] = null;
+    }
+
+    add (data) {
+        const newNode = new LinkedListNode(data);
+
+        if (this[head] === null) {
+            this[head] = newNode;
+        } else {
+            let current = this[head];
+
+            // Go to the end of the list
+            while (current.next !== null) {
+                current = current.next;
+            }
+
+            // On the last node, add the new node
+            current.next = newNode;
+        }
+    }
+
+    get (index) {
+        if ( ! Number(index) < 0) {
+            return undefined;
+        }
+
+        let current = this[head];
+        let i = 0;
+
+        while ((current !== null) && (i < index)) {
+            current = current.next;
+            i++;
+        }
+
+        return current !== null
+            ? current.data
+            : undefined;
+    }
+
+    remove (index) {
+        // Invalid index?
+        if ((this[head] === null) || (index < 0)) {
+            throw new RangeError(`Index ${index} does not exist in the list.`);
+        }
+
+        // Remove the first node
+        if (index === 0) {
+            const data = this[head].data;
+
+            // Replace the head with the next node
+            this[head] = this[head].next;
+
+            return data;
+        }
+
+        let current = this[head];
+        let previous = null;
+        let i = 0;
+
+        while ((current !== null) && (i < index)) {
+            // Save the current value
+            previous = current;
+
+            current = current.next;
+
+            i++;
+        }
+
+        // Remove the node if found
+        if (current !== null) {
+            // skip over the node to "remove" it
+            previous.next = current.next;
+
+            return current.data;
+        }
+
+        throw new RangeError(`Index ${index} does not exist in the list.`);
+    }
+
+    *values () {
+        let current = this[head];
+
+        while (current !== null) {
+            yield current.data;
+            current = current.next;
+        }
+    }
+
+    [Symbol.iterator] () {
+        return this.values();
+    }
+}
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diff --git a/src/usage.js b/src/usage.js
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--- /dev/null
+++ b/src/usage.js
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+import {
+    CircularDoublyLinkedList,
+    DoublyLinkedList,
+    LinkedList,
+} from "./structures/index.js";
+
+function useLinkedList () {
+    console.log('-----------------------------------------------------------------------------------------------------');
+    console.log('Linked List');
+    console.log('-----------------------------------------------------------------------------------------------------');
+    const list = new LinkedList();
+    list.add("red");
+    list.add("orange");
+    list.add("yellow");
+
+    // get the second item in the list
+    console.log('Index 1 in list', list.get(1));
+
+    // print out all the items
+    for (const color of list) {
+        console.log(color);
+    }
+
+    // remove the second item in the list
+    console.log('Removing list item with index 1', list.remove(1));
+
+    // get the item now with index 1
+    console.log('New list item with index 1', list.get(1));
+}
+
+function useDoublyLinkedList () {
+    console.log('-----------------------------------------------------------------------------------------------------');
+    console.log('Doubly-Linked List');
+    console.log('-----------------------------------------------------------------------------------------------------');
+    const list = new DoublyLinkedList();
+    list.add("red");
+    list.add("orange");
+    list.add("yellow");
+
+    console.log('Index 1 in list',list.get(1));
+
+    for (const color of list.reverse()) {
+        console.log(color);
+    }
+
+    // remove the second item in the list
+    console.log('Removing list item with index 1', list.remove(1));
+
+    // get the item now with index 1
+    console.log('New list item with index 1', list.get(1));
+}
+
+function useCircularDoublyLinkedList () {
+    console.log('-----------------------------------------------------------------------------------------------------');
+    console.log('Circular Doubly-Linked List');
+    console.log('-----------------------------------------------------------------------------------------------------');
+
+    const list = new CircularDoublyLinkedList();
+    list.add("red");
+    list.add("orange");
+    list.add("yellow");
+
+    // get the second item in the list
+    console.log('Index 1 in list', list.get(1));       // "orange"
+
+    for (const color of list.values()) {
+        console.log(color);
+    }
+
+    // remove the second item in the list
+    console.log('Removing list item with index 1', list.remove(1));
+
+    // get the item now with index 1
+    console.log('New list item with index 1', list.get(1));
+}
+
+(() => {
+    useLinkedList();
+    console.log('');
+    useDoublyLinkedList();
+    console.log('');
+    useCircularDoublyLinkedList();
+})();
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