feat(LinkedList) add size

Author: amejiarosario

lib/data-structures/linked-lists/linked-list.js

@@ -6,7 +6,8 @@ const Node = require('./node');
 class LinkedList {
   constructor() {
     this.first = null; // head/root element
-    this.last = null;
+    this.last = null; // last element of the list
+    this.size = 0; // total number of elements in the list
   }
 
   /**
@@ -28,6 +29,8 @@ class LinkedList {
       this.last = node;
     }
 
+    this.size++;
+
     return node;
   }
 
@@ -43,6 +46,9 @@ class LinkedList {
       if(this.first) {
         this.first.previous = null;
       }
+
+      this.size--;
+
       return first.value;
     } else {
       this.last = null;
@@ -66,6 +72,7 @@ class LinkedList {
     }
 
     this.first = node; // update head
+    this.size++;
 
     return node;
   }
@@ -92,6 +99,7 @@ class LinkedList {
     }
 
     if(target) {
+      this.size--;
       return target.value;
     }
   }

lib/data-structures/linked-lists/linked-list.spec.js

@@ -103,6 +103,7 @@ describe('LinkedList', function () {
       it('should have a reference to previous node on the last element', () => {
         // expect(linkedList.last.value).toBe('d');
         expect(linkedList.last.previous.value).toBe('c');
+        expect(linkedList.size).toBe(4);
       });
 
       it('should have a reference to previous node on the first element', () => {
@@ -130,10 +131,12 @@ describe('LinkedList', function () {
         expect(linkedList.first.next.previous.value).toBe('b');
         // expect(linkedList.first.value).toBe('b');
         expect(linkedList.first.previous).toBe(null);
+        expect(linkedList.size).toBe(3);
       });
 
       it('should keep previous updated when deleting everything', () => {
         linkedList.removeFirst();
+        expect(linkedList.size).toBe(2);
         // c -> d
         // expect(linkedList.first.value).toBe('c');
         expect(linkedList.first.previous).toBe(null);
@@ -149,6 +152,7 @@ describe('LinkedList', function () {
         expect(linkedList.first).toBe(null);
 
         linkedList.removeFirst();
+        expect(linkedList.size).toBe(0);
       });
     });
 
@@ -162,6 +166,7 @@ describe('LinkedList', function () {
         expect(linkedList.last.value).toBe('b');
         expect(linkedList.last.previous.value).toBe('a');
         expect(linkedList.first.previous).toBe(null);
+        expect(linkedList.size).toBe(2);
       });
     });
 
@@ -174,10 +179,13 @@ describe('LinkedList', function () {
       });
 
       it('should do nothing with previous', () => {
+        expect(linkedList.size).toBe(3);
         expect(linkedList.removeLast()).toBe('c');
         expect(linkedList.pop()).toBe('b');
         expect(linkedList.remove()).toBe('a');
         expect(linkedList.shift()).toBe(undefined);
+        linkedList.removeLast();
+        expect(linkedList.size).toBe(0);
       });
     });
   });