Add fromArray and toArray methods to the linked list class.

Author: stoimen

src/data-structures/linkedList.test.ts

@@ -171,6 +171,96 @@ describe('List', () => {
     })
   })
 
+  describe('fromArray', () => {
+    it('should create a list from an array of elements', () => {
+      const array = [1, 2, 3, 4]
+      const list = new List<number>()
+      list.fromArray(array)
+
+      const result = [] as number[]
+      list.map((node) => result.push(node.data))
+
+      expect(result).toEqual(array)
+    })
+
+    it('should handle an empty array', () => {
+      const array: number[] = []
+      const list = new List<number>()
+      list.fromArray(array)
+
+      expect(list.head).toBeNull()
+      expect(list.tail).toBeNull()
+    })
+
+    it('should correctly set head and tail for a single element array', () => {
+      const array = [42]
+      const list = new List<number>()
+      list.fromArray(array)
+
+      expect(list.head).not.toBeNull()
+      expect(list.tail).not.toBeNull()
+      expect(list.head).toBe(list.tail)
+      expect(list.head?.data).toBe(42)
+    })
+
+    it('should correctly link nodes', () => {
+      const array = [1, 2, 3]
+      const list = new List<number>()
+      list.fromArray(array)
+
+      expect(list.head?.data).toBe(1)
+      expect(list.head?.next?.data).toBe(2)
+      expect(list.head?.next?.next?.data).toBe(3)
+      expect(list.head?.next?.next?.next).toBeNull()
+
+      expect(list.tail?.data).toBe(3)
+      expect(list.tail?.prev?.data).toBe(2)
+      expect(list.tail?.prev?.prev?.data).toBe(1)
+      expect(list.tail?.prev?.prev?.prev).toBeNull()
+    })
+  })
+
+  describe('toArray', () => {
+    it('should return an array of all list nodes\' data', () => {
+      const list = new List<number>()
+      list.push(new Node(1))
+      list.push(new Node(2))
+      list.push(new Node(3))
+
+      const result = list.toArray()
+
+      expect(result).toEqual([1, 2, 3])
+    })
+
+    it('should return an empty array when the list is empty', () => {
+      const list = new List<number>()
+
+      const result = list.toArray()
+
+      expect(result).toEqual([])
+    })
+
+    it('should handle a list with a single node', () => {
+      const list = new List<number>()
+      list.push(new Node(42))
+
+      const result = list.toArray()
+
+      expect(result).toEqual([42])
+    })
+
+    it('should correctly handle a list with multiple nodes', () => {
+      const list = new List<string>()
+      list.push(new Node('a'))
+      list.push(new Node('b'))
+      list.push(new Node('c'))
+
+      const result = list.toArray()
+
+      expect(result).toEqual(['a', 'b', 'c'])
+    })
+  })
+
   describe('toString', () => {
     it('should return a concatenated string of JSON stringified node data', () => {
       const node1 = new Node({ value: 1 })

src/data-structures/linkedList.ts

@@ -126,6 +126,23 @@ class List<T> {
     [left.data, right.data] = [right.data, left.data]
   }
 
+  /**
+   * Fills the List with data from an array.
+   * @param {T[]} array - The array to fill the list with.
+   */
+  fromArray(array: T[]): void {
+    array.forEach((data) => this.push(new Node(data)))
+  }
+
+  /**
+   * @returns {T[]} An array of all list nodes' data.
+   */
+  toArray(): T[] {
+    const array: T[] = []
+    this.map((node) => array.push(node.data))
+    return array
+  } 
+
   /**
    * Returns all list nodes' data concatenated into a single string.
    * @returns {String} The concatenated string of all nodes' data.