英文:
Why am I not able to insert elements into my linked-list implementation?
问题
我正在使用Java实现链表。特别是在进行插入操作时，如果给定的索引超过链表的长度，我必须将值追加到链表中。尽管我已经为此编写了代码，但情况并不是这样发生。
为了调试这个问题，我添加了打印链表的代码行。我可以在插入函数中的条件if(index >= this.length())之前打印列表，但不能在条件内部的代码行中打印链表。
package com.learning.algorithms.LinkedList;
public class Node {
int data;
Node next;
public Node() {
}
public Node(int i) {
this.data = i;
this.next = null;
}
}
package com.learning.algorithms.LinkedList;
public class LinkedList {
Node head;
Node tail;
public LinkedList() {
this.head = new Node();
this.tail = this.head;
}
public LinkedList(int value) {
this.head = new Node();
this.head.data = value;
this.head.next = null;
this.tail = this.head;
}
public LinkedList append(int value) {
Node newNode = new Node(value);
this.tail.next = newNode;
this.tail = newNode;
return this;
}
public void printList() {
Node useNode = this.head;
while (useNode != null) {
System.out.println(useNode.data);
useNode = useNode.next;
}
//print(useNode);
}
private void print(Node useNode) {
if (useNode != null) {
System.out.println(useNode.data);
print(useNode.next);
}
}
public LinkedList prepend(int i) {
Node newNode = new Node(i);
newNode.next = this.head;
this.head = newNode;
return this;
}
public LinkedList insert(int index, int value) {
if (index == 0) {
this.prepend(value);
return this;
}
this.printList();
if (index >= this.length()) {
System.out.println("inside");
this.printList();
this.append(value);
return this;
}
Node nodeJustBeforeGivenIndex = this.head;
// getting node just before given index using while loop
while (index > 1) {
nodeJustBeforeGivenIndex = nodeJustBeforeGivenIndex.next;
index--;
}
// make an insert
Node newNode = new Node(value);
newNode.next = nodeJustBeforeGivenIndex.next;
nodeJustBeforeGivenIndex.next = newNode;
return this;
}
private int length() {
int counnt = 0;
if (this.head != null) {
while (this.head != null) {
this.head = this.head.next;
counnt++;
}
}
return counnt;
}
}
package com.learning.algorithms.LinkedList;
public class LinkedListImplementation {
public static void main(String[] args) {
LinkedList list = new LinkedList(10);
list.append(5);
list.append(16);
list.prepend(1);
list.insert(0, 15);
list.insert(10, 222);
list.printList();
}
}
运行此实现类的控制台输出：
15
1
10
5
16
inside
英文:
I am doing linkedlist implementation in java. Particularly, while doing insert operation, if the given index is more than the length of the linkedlist, I have to append the value to the linkedlist. Though I have written code for the same, it is not happening that way.
In order to debug this, I added lines for printing linkedlist. I could print the list just before the condition if(index >= this.length()) in the insert function but not able to print the linkedlist in the line inside the condition.
package com.learning.algorithms.LinkedList;
public class Node {
int data;
Node next;
public Node() {
}
public Node(int i) {
this.data = i;
this.next = null;
}
}
package com.learning.algorithms.LinkedList;
public class LinkedList {
Node head;
Node tail;
public LinkedList() {
this.head = new Node();
this.tail = this.head;
}
public LinkedList(int value) {
this.head = new Node();
this.head.data = value;
this.head.next = null;
this.tail = this.head;
}
public LinkedList append(int value) {
Node newNode = new Node(value);
this.tail.next = newNode;
this.tail = newNode;
return this;
}
public void printList() {
Node useNode = this.head;
while(useNode!=null)
{
System.out.println(useNode.data);
useNode = useNode.next;
}
//print(useNode);
}
private void print(Node useNode) {
if(useNode!=null)
{
System.out.println(useNode.data);
print(useNode.next);
}
}
public LinkedList prepend(int i) {
Node newNode = new Node(i);
newNode.next = this.head;
this.head = newNode;
return this;
}
public LinkedList insert(int index, int value) {
if(index == 0)
{
this.prepend(value);
return this;
}
this.printList();
if(index >= this.length())
{
System.out.println("inside");
this.printList();
this.append(value);
return this;
}
Node nodeJustBeforeGivenIndex = this.head;
// getting node just before given index using while loop
while(index>1)
{
nodeJustBeforeGivenIndex = nodeJustBeforeGivenIndex.next;
index--;
}
// make an insert
Node newNode = new Node(value);
newNode.next = nodeJustBeforeGivenIndex.next;
nodeJustBeforeGivenIndex.next = newNode;
return this;
}
private int length() {
int counnt = 0;
if(this.head !=null ) {
while(this.head !=null )
{
this.head = this.head.next;
counnt++;
}
}
return counnt;
}
}
package com.learning.algorithms.LinkedList;
public class LinkedListImplementation {
public static void main(String[] args)
{
LinkedList list = new LinkedList(10);
list.append(5);
list.append(16);
list.prepend(1);
list.insert(0, 15);
list.insert(10, 222);
list.printList();
}
}
Console output for running this implementation class:
15
1
10
5
16
inside
答案1
得分: 1
你不应该在 length 方法内部修改头部值。
这样会修复它：
private int length() {
int count = 0;
Node iter = this.head;
while(iter != null) {
iter = iter.next;
count++;
}
return count;
}
仅注释掉 insert 方法内的两条打印语句，输出将会是：
inside
15
1
10
5
16
222
英文:
You should not modify the head value inside the length method.
This will fix it:
private int length() {
int counnt = 0;
Node iter = this.head;
while(iter !=null )
{
iter = iter.next;
counnt++;
}
return counnt;
}
Commenting just the two print stamtents inside insert, the output gets to be:
inside
15
1
10
5
16
222
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