Ll kth from end

.eslintrc.json

@@ -0,0 +1,27 @@
+{
+    "env": {
+      "browser": true,
+      "node": true,
+      "commonjs": true,
+      "jest": true,
+      "es6": true
+    },
+    "globals": {
+      "err": true,
+      "req": true,
+      "res": true,
+      "next": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+      "sourceType": "module"
+    },
+    "rules": {
+      "no-console": "off",
+      "indent": [ "error", 2 ],
+      "quotes": ["error", "single", { "allowTemplateLiterals": true }],
+      "comma-dangle": ["error", "always-multiline"],
+      "semi": [ "error", "always" ]
+    }
+  }
+

README.md

@@ -1,6 +1,14 @@
-# Table of Contents
-[1- code challange class 2 array shift ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/3)
+# k-th value from the end of a linked list
+## challange summary 
+create a linked list then create a method that do what supposed  to do then test it
+
+## Challenge description
+Write a method for the Linked List class which takes a number, k, as a parameter. Return the node’s value that is k from the end of the linked list. You have access to the Node class and all the properties on the Linked List class as well as the methods created in previous challenges.
+
+## Approach & Efficiency
+Write a method for the Linked List class which takes a number, k, as a parameter. Return the node’s value that is k from the end of the linked list.
+## Solution
+
+![UML](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/blob/ll-kth-from-end/20200204_140847.jpg)
 
-[2- code challange class 3 array binary search ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/2)
 
-[

challanges/ll-kth-from-end/ll-kth-from-end.js

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+'use strict';
+
+class Node {
+  constructor(value) {
+    this.value = value;
+    this.next = null;
+  }
+
+}
+
+class LinkedList {
+  constructor() {
+    this.head = null;
+  }
+
+  append (value) {
+    let node  = new Node(value);
+    if(!this.head){
+      this.head = node;
+      return this;
+    }
+    let currentNode = this.head;
+    while(currentNode.next){
+      currentNode = currentNode.next;
+    }
+    currentNode.next = node;
+    return this;
+  }
+
+  kthFromEnd(k){
+    let currentNode = this.head;
+    let length = 0;
+    while(currentNode){
+      length++;
+      currentNode = currentNode.next;
+    }
+    let i = length - 1 - k;
+    if(i < 0 || k < 0){
+      return 'exception';
+    }
+    currentNode = this.head;
+    while(i > 0){
+      i--;
+      currentNode = currentNode.next;
+    }
+    return currentNode.value;
+  }
+
+}
+module.exports = LinkedList;

challanges/ll-kth-from-end/ll-kth-from-end.test.js

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+'use strict';
+const  LinkedList = require('./ll-kth-from-end.js');
+describe('Linked list  Module',()=>{
+  it ('constructor',()=>{
+    let list = new LinkedList();
+    expect(list.head).toBeNull();
+
+  });
+  it('append ()',()=>{
+    let ll = new LinkedList();
+    let initVal = '1';
+    ll.append(initVal);
+    expect(ll.head.value).toEqual(initVal);
+    expect(ll.head.value.next).toBeAnObject;
+    let secondVal = '2';
+    ll.append(secondVal);
+    expect(ll.head.value).toEqual(initVal);
+    expect(ll.head.next.value).toEqual(secondVal);
+
+  });
+  it('Where k is greater than the length of the linked list',()=>{
+    let ll = new LinkedList();
+    ll.append(1);
+    ll.append(3);
+    expect(ll.kthFromEnd(5)).toMatch('exception');
+
+  });
+  it('Where k and the length of the list are the same',()=>{
+    let ll = new LinkedList();
+    ll.append(1);
+    ll.append(3);
+    expect(ll.kthFromEnd(2)).toMatch('exception');
+  });
+  it('Where k is not a positive integer',()=>{
+    let ll = new LinkedList();
+    ll.append(1);
+    ll.append(3);
+    expect(ll.kthFromEnd(-2)).toMatch('exception');
+  });
+  it('Where the linked list is of a size 1',()=>{
+    let ll = new LinkedList();
+    ll.append(5);
+    expect(ll.kthFromEnd(1)).toMatch('exception');
+  });
+  it('“Happy Path” where k is not at the end, but somewhere in the middle of the linked list',()=>{
+    let list = new LinkedList();
+    list.append(1);
+    list.append(3);
+    list.append('5');
+    list.append(7);
+    list.append(9);
+    expect(list.kthFromEnd(2)).toMatch('5');
+  });
+});