Add getValues() method to HashTable and update LinkedList READMEs.

Author: trekhleb

src/data-structures/doubly-linked-list/README.md

@@ -12,7 +12,7 @@ consists of a set of sequentially linked records called nodes. Each node contain
 two fields, called links, that are references to the previous and to the next 
 node in the sequence of nodes. The beginning and ending nodes' previous and next 
 links, respectively, point to some kind of terminator, typically a sentinel 
-node or null, to facilitate traversal of the list. If there is only one 
+node or null, to facilitate the traversal of the list. If there is only one 
 sentinel node, then the list is circularly linked via the sentinel node. It can 
 be conceptualized as two singly linked lists formed from the same data items, 
 but in opposite sequential orders.

src/data-structures/hash-table/HashTable.js

@@ -107,14 +107,15 @@ export default class HashTable {
   }
 
   /**
-   * Gets the list of all the stored values in the hash table in the order of
-   * the keys map.
+   * Gets the list of all the stored values in the hash table.
    *
    * @return {*[]}
    */
   getValues() {
-    const keys = this.getKeys();
-
-    return keys.map(key => this.buckets[this.hash(key)].head.value.value);
+    return this.buckets.reduce((values, bucket) => {
+      const bucketValues = bucket.toArray()
+        .map((linkedListNode) => linkedListNode.value.value);
+      return values.concat(bucketValues);
+    }, []);
   }
 }

src/data-structures/hash-table/__test__/HashTable.test.js

@@ -94,6 +94,24 @@ describe('HashTable', () => {
     hashTable.set('b', 'beta');
     hashTable.set('c', 'gamma');
 
-    expect(hashTable.getValues()).toEqual(['alpha', 'beta', 'gamma']);
+    expect(hashTable.getValues()).toEqual(['gamma', 'alpha', 'beta']);
+  });
+
+  it('should get all the values from empty hash table', () => {
+    const hashTable = new HashTable();
+    expect(hashTable.getValues()).toEqual([]);
+  });
+
+  it('should get all the values in case of hash collision', () => {
+    const hashTable = new HashTable(3);
+
+    // Keys `ab` and `ba` in current implementation should result in one hash (one bucket).
+    // We need to make sure that several items from one bucket will be serialized.
+    hashTable.set('ab', 'one');
+    hashTable.set('ba', 'two');
+
+    hashTable.set('ac', 'three');
+
+    expect(hashTable.getValues()).toEqual(['one', 'two', 'three']);
   });
 });

src/data-structures/linked-list/README.md

@@ -4,7 +4,8 @@ _Read this in other languages:_
 [_简体中文_](README.zh-CN.md),
 [_Русский_](README.ru-RU.md),
 [_日本語_](README.ja-JP.md),
-[_Português_](README.pt-BR.md)
+[_Português_](README.pt-BR.md),
+[_한국어_](README.ko-KR.md)
 
 In computer science, a **linked list** is a linear collection 
 of data elements, in which linear order is not given by