Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit 7deaaac

Browse files
Doubly linked list
1 parent cdc00f1 commit 7deaaac

File tree

4 files changed

+302
-2
lines changed

4 files changed

+302
-2
lines changed

‎src/main/kotlin/pl/dmichalski/algorithms/data_structures/_1_singly_linked_list/Runner.kt‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -31,7 +31,7 @@ object Runner {
3131
println("------------------ Getting the last element ------------------")
3232
singlyLinkedList = getSinglyLinkedLit()
3333
val lastElement = singlyLinkedList.get(singlyLinkedList.getLength() - 1)
34-
println("lastElement = ${lastElement}")
34+
println("lastElement = $lastElement")
3535

3636
println("\n------------------ Setting new first element ------------------ ")
3737
singlyLinkedList = getSinglyLinkedLit()
@@ -60,7 +60,7 @@ object Runner {
6060
singlyLinkedList.push("first")
6161
singlyLinkedList.push("second")
6262

63-
return singlyLinkedList;
63+
return singlyLinkedList
6464
}
6565

6666
private fun printList(singlyLinkedList: SinglyLinkedList) {
Lines changed: 191 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,191 @@
1+
package pl.dmichalski.algorithms.data_structures._2_doubly_linked_list
2+
3+
class DoublyLinkedList {
4+
5+
private var head: Node?
6+
private var tail: Node?
7+
private var length: Int
8+
9+
init {
10+
this.head = null
11+
this.tail = null
12+
this.length = 0
13+
}
14+
15+
fun push(value: String) {
16+
val newNode = Node(value)
17+
if (this.head == null) {
18+
this.head = newNode
19+
this.tail = newNode
20+
} else {
21+
this.tail!!.setNext(newNode)
22+
newNode.setPrevious(this.tail)
23+
this.tail = newNode
24+
}
25+
length++
26+
}
27+
28+
fun pop() {
29+
if (length == 0) {
30+
return
31+
}
32+
33+
val nodeToRemove = tail
34+
35+
if (length == 1) {
36+
this.head = null
37+
this.tail = null
38+
} else {
39+
this.tail = nodeToRemove!!.getPrevious()
40+
this.tail!!.setNext(null)
41+
nodeToRemove.setPrevious(null)
42+
}
43+
44+
length--
45+
}
46+
47+
fun shift() {
48+
if (length == 0) {
49+
return
50+
}
51+
52+
val oldHead = head
53+
if (this.length == 1) {
54+
this.head = null
55+
this.tail = null
56+
}
57+
head = oldHead!!.getNext()
58+
this.head!!.setPrevious(null)
59+
oldHead.setNext(null)
60+
61+
length--
62+
}
63+
64+
fun unshift(value: String) {
65+
val newNode = Node(value)
66+
67+
if (this.head == null) {
68+
this.head = newNode
69+
this.tail = newNode
70+
} else {
71+
head!!.setPrevious(newNode)
72+
newNode.setNext(head)
73+
head = newNode
74+
}
75+
76+
length++
77+
}
78+
79+
fun get(index: Int): Node? {
80+
if (index < 0 || index >= length) {
81+
return null
82+
}
83+
84+
var currentIndex: Int?
85+
var current: Node?
86+
87+
if (index <= length / 2) {
88+
currentIndex = 0
89+
current = head
90+
91+
while (currentIndex != index) {
92+
current = current!!.getNext()
93+
currentIndex++
94+
}
95+
} else {
96+
currentIndex = length - 1
97+
current = tail
98+
99+
while (currentIndex != index) {
100+
current = current!!.getPrevious()
101+
currentIndex--
102+
}
103+
}
104+
105+
return current
106+
}
107+
108+
fun set(value: String, index: Int): Boolean {
109+
val node = get(index)
110+
return if (node != null) {
111+
node.setValue(value)
112+
true
113+
} else {
114+
false
115+
}
116+
}
117+
118+
fun insert(value: String, index: Int): Boolean {
119+
if (index < 0 || index > length) {
120+
return false
121+
}
122+
123+
if (index == 0) {
124+
this.unshift(value)
125+
return true
126+
}
127+
128+
if (index == length) {
129+
this.push(value)
130+
return true
131+
}
132+
133+
val newNode = Node(value)
134+
val previous = this.get(index - 1)
135+
val nextNode = previous!!.getNext()
136+
137+
previous.setNext(newNode)
138+
newNode.setPrevious(previous)
139+
140+
newNode.setNext(nextNode)
141+
newNode.setPrevious(newNode)
142+
length++
143+
return true
144+
}
145+
146+
fun remove(index: Int): Node? {
147+
if (index < 0 || index >= length) {
148+
return null
149+
}
150+
151+
if (index == 0) {
152+
val firstElement = head
153+
shift()
154+
return firstElement
155+
}
156+
157+
if (index == length - 1) {
158+
val lastElement = tail
159+
pop()
160+
return lastElement
161+
}
162+
163+
val elementToRemove = get(index)
164+
elementToRemove!!.getPrevious()!!.setNext(elementToRemove.getNext())
165+
elementToRemove.getNext()!!.setPrevious(elementToRemove.getPrevious())
166+
167+
elementToRemove.setPrevious(null)
168+
elementToRemove.setNext(null)
169+
170+
length--
171+
return elementToRemove
172+
}
173+
174+
fun getHead(): Node? {
175+
return head
176+
}
177+
178+
fun getTail(): Node? {
179+
return tail
180+
}
181+
182+
fun getLength(): Int {
183+
return length
184+
}
185+
186+
override fun toString(): String {
187+
return "Head: $head\n" +
188+
"Tail: $tail\n" +
189+
"Length: $length\n"
190+
}
191+
}
Lines changed: 44 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,44 @@
1+
package pl.dmichalski.algorithms.data_structures._2_doubly_linked_list
2+
3+
class Node(private var value: String) {
4+
5+
private var previous: Node?
6+
private var next: Node?
7+
8+
init {
9+
this.previous = null
10+
this.next = null
11+
}
12+
13+
fun getValue(): String {
14+
return value
15+
}
16+
17+
fun setValue(value: String) {
18+
this.value = value
19+
}
20+
21+
fun getPrevious(): Node? {
22+
return previous
23+
}
24+
25+
fun setPrevious(previousNode: Node?) {
26+
previous = previousNode
27+
}
28+
29+
fun getNext(): Node? {
30+
return next
31+
}
32+
33+
fun setNext(nextNode: Node?) {
34+
next = nextNode
35+
}
36+
37+
override fun toString(): String {
38+
return "Node(value='$value', " +
39+
"previousValue=${previous?.getValue()}, " +
40+
"nextValue=${next?.getValue()})"
41+
}
42+
43+
44+
}
Lines changed: 65 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,65 @@
1+
package pl.dmichalski.algorithms.data_structures._2_doubly_linked_list
2+
3+
object Runner {
4+
5+
@JvmStatic
6+
fun main(args: Array<String>) {
7+
println("------------------ Initial doubly linked list ------------------ ")
8+
var doublyLinkedList = getDoublyLinkedLit()
9+
printList(doublyLinkedList)
10+
11+
println("------------------ After adding third element to the end ------------------ ")
12+
doublyLinkedList = getDoublyLinkedLit()
13+
doublyLinkedList.push("third")
14+
printList(doublyLinkedList)
15+
16+
println("------------------ After removing last element ------------------ ")
17+
doublyLinkedList = getDoublyLinkedLit()
18+
doublyLinkedList.pop()
19+
printList(doublyLinkedList)
20+
21+
println("------------------ After removing first element ------------------ ")
22+
doublyLinkedList = getDoublyLinkedLit()
23+
doublyLinkedList.shift()
24+
printList(doublyLinkedList)
25+
26+
println("------------------ After adding element to the beginning ------------------ ")
27+
doublyLinkedList = getDoublyLinkedLit()
28+
doublyLinkedList.unshift("before first")
29+
printList(doublyLinkedList)
30+
31+
println("------------------ Getting the last element ------------------")
32+
doublyLinkedList = getDoublyLinkedLit()
33+
val lastElement = doublyLinkedList.get(doublyLinkedList.getLength() - 1)
34+
println("lastElement = ${lastElement}")
35+
36+
println("\n------------------ Setting new first element ------------------ ")
37+
doublyLinkedList = getDoublyLinkedLit()
38+
doublyLinkedList.set("new first", 0)
39+
printList(doublyLinkedList)
40+
41+
println("------------------ Insert element to the beginning ------------------ ")
42+
doublyLinkedList = getDoublyLinkedLit()
43+
doublyLinkedList.insert("before first", 0)
44+
printList(doublyLinkedList)
45+
46+
println("------------------ Removing first element ------------------ ")
47+
doublyLinkedList = getDoublyLinkedLit()
48+
doublyLinkedList.remove(0)
49+
printList(doublyLinkedList)
50+
}
51+
52+
private fun getDoublyLinkedLit(): DoublyLinkedList {
53+
val doublyLinkedList = DoublyLinkedList()
54+
55+
doublyLinkedList.push("first")
56+
doublyLinkedList.push("second")
57+
58+
return doublyLinkedList;
59+
}
60+
61+
private fun printList(doublyLinkedList: DoublyLinkedList) {
62+
println(doublyLinkedList)
63+
}
64+
65+
}

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /