Java 从零开始排序插入到单链表中
我一直在尝试从头开始创建一个排序链表,它只接受字符串,但在插入时对其进行排序。这是我目前的代码:Java 从零开始排序插入到单链表中,java,sorting,singly-linked-list,Java,Sorting,Singly Linked List,我一直在尝试从头开始创建一个排序链表,它只接受字符串,但在插入时对其进行排序。这是我目前的代码: import java.util.Arrays; public class SortedLinkedList { private StringNode head = null; /** * Default Constructor for a sorted linked list */ public SortedLinkedList() {}
import java.util.Arrays;
public class SortedLinkedList {
private StringNode head = null;
/**
* Default Constructor for a sorted linked list
*/
public SortedLinkedList() {}
/**
* Will add a new node with the specified data to the correctly sorted
* position in the list
*/
public void add(String data) {
if (head == null) {
head = new StringNode(data);
}
StringNode temp = new StringNode(data);
StringNode current = head;
if (current != null) {
while (current.getNext() != null) {
if (current.getData().toString().compareTo(current.getNext().getData().toString()) < 0) {
temp.setNext(current.getNext());
current.setNext(temp);
} else
current.setNext(temp);
}
}
}
/**
* Will remove the node that matches the specified data from the list.
* Returns true if node is found, otherwise will return false
*/
public boolean remove(String data) {
StringNode current = head;
if (head != null) {
while (current.getNext() != null) {
if (current.getData().toString().equals(data)) {
current.setNext(current.getNext().getNext());
return true;
}
current = current.getNext();
}
}
return false;
}
/**
* Will cycle through the list and display each item on a new line
*/
public void display() {
if (head != null) {
StringNode current = head.getNext();
System.out.print("[");
while (current.getNext() != null) {
System.out.print(current.getData().toString() + ", ");
current = current.getNext();
}
System.out.print("]");
}
}
// Inner Class
class StringNode {
String data;
StringNode next;
public StringNode(String nodeData) {
next = null;
data = nodeData;
}
/**
* Getter of Data
*/
public String getData() {
return data;
}
/**
* Getter of Next
*/
public StringNode getNext() {
return next;
}
/**
* Setter of Data
*/
public void setData(String newData) {
data = newData;
}
/**
* Setter of Next
*/
public void setNext(StringNode nextNode) {
next = nextNode;
}
}
}
是显示方法第70行中的空指针异常,这是while循环的创建。我完全迷路了,需要一些指导。谢谢。由于最后一个元素的.getNext()为null,您实际上需要检查current==null
while (current != null)
稍微重构一下:
// should print [] for empty SLL; no dangling comma
public void display() {
String out = "[";
StringNode current = head;
while(current != null) {
out = out + current.getData();
current = current.getNext();
if (current != null)
out = out + ", ";
}
out += "]";
System.out.print(out);
}
编辑:此外,您的添加/删除方法需要重新修改。。。试着在纸上一步一步地检查算法,然后将条件/操作转换为Java
例如:
/**
* Will add a new node with the specified data to the correctly sorted
* position in the list
*/
public void add(String data) {
StringNode temp = new StringNode(data);
if(head == null) {
head = temp;
return; // only adding one node
}
StringNode previous = head;
if (data.compareTo(previous.getData()) < 0) {
head = temp; // temp < head, so we add it to the beginning
head.setNext(previous);
return; // done
}
StringNode current = previous.getNext();
while (current != null) {
if (data.compareTo(current.getData()) < 0) {
temp.setNext(current);
previous.setNext(temp);
return; // done
} else {
previous = current;
current = previous.getNext();
}
}
// current == null, so we reached the end of the list;
previous.setNext(temp);
}
/**
*将使用指定的数据将新节点添加到正确排序的
*排名
*/
公共void添加(字符串数据){
StringNode temp=新StringNode(数据);
if(head==null){
压头=温度;
return;//仅添加一个节点
}
StringNode-previous=头部;
if(data.compareTo(previous.getData())<0){
head=temp;//temp
您实际上想要检查current==null,因为最后一个元素的.getNext()为null
while (current != null)
稍微重构一下:
// should print [] for empty SLL; no dangling comma
public void display() {
String out = "[";
StringNode current = head;
while(current != null) {
out = out + current.getData();
current = current.getNext();
if (current != null)
out = out + ", ";
}
out += "]";
System.out.print(out);
}
编辑:此外,您的添加/删除方法需要重新修改。。。试着在纸上一步一步地检查算法,然后将条件/操作转换为Java
例如:
/**
* Will add a new node with the specified data to the correctly sorted
* position in the list
*/
public void add(String data) {
StringNode temp = new StringNode(data);
if(head == null) {
head = temp;
return; // only adding one node
}
StringNode previous = head;
if (data.compareTo(previous.getData()) < 0) {
head = temp; // temp < head, so we add it to the beginning
head.setNext(previous);
return; // done
}
StringNode current = previous.getNext();
while (current != null) {
if (data.compareTo(current.getData()) < 0) {
temp.setNext(current);
previous.setNext(temp);
return; // done
} else {
previous = current;
current = previous.getNext();
}
}
// current == null, so we reached the end of the list;
previous.setNext(temp);
}
/**
*将使用指定的数据将新节点添加到正确排序的
*排名
*/
公共void添加(字符串数据){
StringNode temp=新StringNode(数据);
if(head==null){
压头=温度;
return;//仅添加一个节点
}
StringNode-previous=头部;
if(data.compareTo(previous.getData())<0){
head=temp;//temp
我对您的代码进行了一些重构,并删除了您编写的代码注释。
相反,我添加了一些我自己的评论
请参阅这些注释,并考虑为编写的任何代码编写单元测试。它将帮助您捕获任何bug,并让您对正在发布的代码充满信心
package com.so36046948;
public class SortedLinkedList {
private StringNode head = null;
public SortedLinkedList() {}
public void add(String data) {
// Do null checks on Data.
if (head == null) {
// If we have no head, set head and return immediately.
head = new StringNode(data, null);
return;
}
StringNode previous = head;
StringNode current = head;
StringNode temp = new StringNode(data);
// Continue iterating till we reach the end of the list.
while (null != current) {
if (current.getData().compareTo(data) < 0) {
if (current == head) {
// Special handling for the case when the element being inserted is greater than head.
head = temp;
temp.setNext(current);
return;
}
break;
}
previous = current;
current = current.getNext();
}
// Break out of the while loop and reset the next pointers. Previous points to immediate
// greater element and current points to immediate element that is less than *data* being
// inserted.
previous.setNext(temp);
temp.setNext(current);
}
public void display() {
// Consider overriding toString method instead of creating a display method,
if (null == head) {
System.out.println("List is empty.");
return;
}
StringBuilder sb = new StringBuilder();
StringNode current = head;
sb.append("[");
while (current != null) {
sb.append(current.getData()).append(",");
current = current.getNext();
}
sb.append("]");
System.out.println(sb);
}
// Inner Class
class StringNode {
private final String data;
private StringNode next;
public StringNode(String nodeData) {
next = null;
data = nodeData;
}
public StringNode(String nodeData, StringNode next) {
this.next = next;
data = nodeData;
}
/**
* Getter of Data
*/
public String getData() {
return data;
}
/**
* Getter of Next
*/
public StringNode getNext() {
return next;
}
/**
* Setter of Next
*/
public void setNext(StringNode nextNode) {
next = nextNode;
}
}
public static void main(String[] args) {
// Consider writing unit tests. I have created skeletons of a few rudimentry tests,
// you may add more.
test_insertInDscendingOrder();
test_insertInAscendingOrder();
test_insertTwoElements();
test_insertSingleElement();
//test_insertNullData();
}
private static void test_insertInDscendingOrder() {
SortedLinkedList name = new SortedLinkedList();
name.add("v");name.add("b");name.add("a");name.display();
}
private static void test_insertInAscendingOrder() {
SortedLinkedList name = new SortedLinkedList();
name.add("a");name.add("b");name.add("c");name.add("d");
name.display();
}
private static void test_insertTwoElements() {
SortedLinkedList name = new SortedLinkedList();
name.add("a");name.add("b");name.display();
}
private static void test_insertSingleElement() {
SortedLinkedList name = new SortedLinkedList();
name.add("a");name.display();
}
private static void test_insertNullData() {
// This would fail, Consider handling null data.
SortedLinkedList name = new SortedLinkedList();
name.add("a");
name.add(null);
name.display();
}
}
package com.so36046948;
公共类分类链接列表{
私有StringNode头=null;
公共分类链接列表(){}
公共void添加(字符串数据){
//对数据执行空检查。
if(head==null){
//如果我们没有头颅,那就定下头颅,马上回来。
head=新的StringNode(数据,null);
返回;
}
StringNode-previous=头部;
StringNode电流=磁头;
StringNode temp=新StringNode(数据);
//继续迭代,直到到达列表的末尾。
while(null!=当前){
if(current.getData().compareTo(data)<0){
如果(当前==水头){
//插入的元件大于头部时的特殊处理。
压头=温度;
温度设置下一步(当前);
返回;
}
打破
}
先前=当前;
current=current.getNext();
}
//中断while循环并重置下一个指针。将上一个指针重置为立即指针
//较大元素和当前元素指向小于*数据*的立即元素
//插入。
上一个。设置下一个(临时);
温度设置下一步(当前);
}
公共空间显示(){
/考虑重写ToStin方法,而不是创建显示方法,
if(null==头){
System.out.println(“列表为空”);
返回;
}
StringBuilder sb=新的StringBuilder();
StringNode电流=磁头;
某人加上(“[”);
while(当前!=null){
sb.append(current.getData()).append(“,”);
current=current.getNext();
}
某人加上(“]”);
系统输出打印LN(sb);
}
//内部阶级
类StringNode{
私有最终字符串数据;
私有节点下一步;
公共StringNode(字符串节点数据){
next=null;
数据=节点数据;
}
公共StringNode(字符串节点数据,StringNode下一个){
this.next=next;
数据=节点数据;
}
/**
*数据获取者
*/
公共字符串getData(){
返回数据;
}
/**
*下一代的获得者
*/
公共StringNode getNext(){
下一步返回;
}
/**
*下一步的制定者
*/
公共void setNext(StringNode nextNode){
next=nextNode;
}
}
公共静态void main(字符串[]args){
/考虑编写单元测试。我已经创建了几个基本入门测试的骨架,
//你可以再加一点。
测试_insertInDscendingOrder();
测试_insertInAscendingOrder();
test_inserttwonents();
test_insertSingleElement();
//test_insertNullData();
}
专用静态无效测试\u insertInDscendingOrder(){
SortedLinkedList name=新的SortedLinkedList();
name.add(“v”);name.add(“b”);name.add(“a”);name.display();
}
专用静态无效测试_insertInAscendingOrder(){
SortedLinkedList name=新的SortedLinkedList();
名称。添加(“a”);名称。添加(“b”);名称。添加(“c”);名称。添加(“d”);
name.display();
}
专用静态空隙试验\u insertTw