@@ -8,32 +8,40 @@ class Node {
88class LinkedList {
99 constructor ( ) {
1010 this . head = null ;
11+ this . tail = null ;
12+ this . size = 0 ;
1113 }
1214
1315 addAtBeginning ( element ) {
1416 this . head = new Node ( element , this . head ) ;
17+ if ( ! this . tail ) {
18+ this . tail = this . head ;
19+ }
20+ this . size += 1 ;
21+ return this . head ;
1522 }
1623
1724 addAtEnd ( element ) {
18- const node = new Node ( element , null ) ;
19- 2025 if ( ! this . head ) {
21- this . head = node ;
22- } else {
23- let address = this . head ;
24- while ( address . next ) {
25- address = address . next ;
26- }
27- address . next = node ;
26+ return this . addAtBeginning ( element ) ;
2827 }
28+ const node = new Node ( element , null ) ;
29+ this . tail . next = node ;
30+ this . tail = node ;
31+ this . size += 1 ;
32+ return node ;
2933 }
3034
3135 removeFromBeginning ( ) {
3236 if ( ! this . head ) {
3337 return null ;
3438 }
39+ if ( this . head . next === null ) {
40+ this . tail = this . head ;
41+ }
3542 const node = this . head ;
3643 this . head = this . head . next ;
44+ this . size -= 1 ;
3745 return node ;
3846 }
3947
@@ -47,8 +55,11 @@ class LinkedList {
4755 address = address . next ;
4856 }
4957
50- const node = address . next ;
51- address . next = null ;
58+ this . tail = address ;
59+ 60+ const node = this . tail . next ;
61+ this . tail . next = null ;
62+ this . size -= 1 ;
5263 return node ;
5364 }
5465
@@ -63,11 +74,7 @@ class LinkedList {
6374 if ( ! this . head ) {
6475 return null ;
6576 }
66- let address = this . head ;
67- while ( address . next ) {
68- address = address . next ;
69- }
70- return address ;
77+ return this . tail ;
7178 }
7279
7380 getAt ( index ) {
@@ -104,8 +111,10 @@ class LinkedList {
104111 count -= 1 ;
105112 }
106113
107- previous . next = new Node ( element , previous . next ) ;
108- return null ;
114+ const node = new Node ( element , previous . next ) ;
115+ previous . next = node ;
116+ this . size += 1 ;
117+ return node ;
109118 }
110119
111120 removeAt ( index ) {
@@ -129,21 +138,18 @@ class LinkedList {
129138
130139 const node = address ;
131140 previous . next = address . next . next ;
141+ this . size -= 1 ;
132142 return node ;
133143 }
134144
135145 length ( ) {
136- let address = this . head ;
137- let count = 0 ;
138- while ( address ) {
139- count += 1 ;
140- address = address . next ;
141- }
142- return count ;
146+ return this . size ;
143147 }
144148
145149 delete ( ) {
146150 this . head = null ;
151+ this . tail = this . head ;
152+ this . size = 0 ;
147153 }
148154}
149155
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