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LinkedList.java
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LinkedList.java
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package com.brian.portfolio.datastructures;
import java.util.NoSuchElementException;
public class LinkedList {
private Node first; //head
private Node last; //tail
private int count;
public void addFirst(int value) {
count++;
var node = new Node(value);
if (isEmpty())
first = last = node;
else {
node.next = first;
first = node;
}
}
public void removeFirst() {
if (isEmpty())
throw new NoSuchElementException();
count--;
if (first == last) {
first = last = null;
return;
}
var second = first.next;
first.next = null;
first = second;
}
public void addLast(int value) {
count++;
var node = new Node(value);
if (isEmpty())
first = last = node;
else {
last.next = node;
last = node;
}
}
public void removeLast() {
if (isEmpty())
throw new NoSuchElementException();
count--;
if (first == last) {
first = last = null;
return;
}
var previous = getPrevious(last);
last = previous;
last.next = null;
}
public int indexOf(int value) {
byte index = 0;
while (first != null) {
if (first.value == value) return index;
index++;
first = first.next;
}
return -1;
}
public int size() {
return count;
}
public boolean contains (int value) {
while (first != null) {
if (first.value == value) return true;
first = first.next;
}
return false;
}
public void reverse() {
if (isEmpty()) return;
var previous = first;
var current = first.next;
while (current != null) {
var next = current.next;
current.next = previous;
previous = current;
current = next;
}
last = first;
last.next = null;
first = previous;
}
public int getKthFromTheEnd(int k) {
if (isEmpty())
throw new IllegalStateException();
var a = first;
var b = first;
for (int i = 0; i < k - 1; i++) {
b = b.next;
if (b.next == null)
throw new IllegalArgumentException();
}
while (b != last) {
a = a.next;
b = b.next;
}
return a.value;
}
public boolean hasLoop() {
var a = first;
var b = first;
if (isEmpty())
throw new IllegalStateException();
while (b != null) {
a = a.next;
b = b.next.next;
if (b == null)
return false;
}
return true;
}
public void printMiddle() {
var a = first;
var b = first;
if (isEmpty())
throw new IllegalStateException();
while (b != last && b.next != last ) {
b = b.next.next;
a = a.next;
}
if (b == last)
System.out.println(a.value);
else
System.out.println(a.value + " & " + a.next.value);
}
public int[] toArray() {
int index = 0;
int[] array = new int[count];
if (isEmpty())
throw new NoSuchElementException();
while (!isEmpty()) {
array[index++] = first.value;
first = first.next;
}
return array;
}
private boolean isEmpty() {
return (first == null);
}
private Node getPrevious(Node node) {
var current = first;
while (current != null) {
if (current.next == node) return current;
current = current.next;
}
return null;
}
private class Node {
private int value;
private Node next;
public Node(int value) {
this.value = value;
}
}
}