我正在尝试开发一种方法，该方法将在链接列表中的当前节点之前插入传递给它的节点。它有3个条件。对于此实现，不能有任何头节点(仅对列表中第一个节点的引用)，并且我无法添加更多变量。
- 如果列表为空，则将传递的节点设置为列表中的第一个节点。
- 如果当前节点位于列表的前面。如果是，则将传递的节点的next设置为当前节点，并将第一个节点设置为传递的节点，将其移动到前面。
- 如果链表不为空且当前节点不在前面，则迭代链表，直到本地节点等于链表的当前节点。然后我执行与 2 中相同的指令。
这是我的代码。
public class LinkedList
{
private Node currentNode;
private Node firstNode;
private int nodeCount;
public static void main(String[] args)
{
LinkedList test;
String dataTest;
test = new LinkedList();
dataTest = "abcdefghijklmnopqrstuvwxyz";
for(int i=0; i< dataTest.length(); i++) { test.insert(new String(new char[] { dataTest.charAt(i) })); }
System.out.println("[1] "+ test);
for(int i=0; i< dataTest.length(); i++) { test.deleteCurrentNode(); }
System.out.println("[2] "+test);
for(int i=0; i< dataTest.length(); i++)
{
test.insertBeforeCurrentNode(new String(new char[] { dataTest.charAt(i) }));
if(i%2 == 0) { test.first(); } else { test.last(); }
}
System.out.println("[3] "+test);
}
public LinkedList()
{
setListPtr(null);
setCurrent(null);
nodeCount = 0;
}
public boolean atEnd()
{
checkCurrent();
return getCurrent().getNext() == null;
}
public boolean isEmpty()
{
return getListPtr() == null;
}
public void first()
{
setCurrent(getListPtr());
}
public void next()
{
checkCurrent();
if (atEnd()) {throw new InvalidPositionInListException("You are at the end of the list. There is no next node. next().");}
setCurrent(this.currentNode.getNext());
}
public void last()
{
if (isEmpty()) {throw new ListEmptyException("The list is currently empty! last()");}
while (!atEnd())
{
setCurrent(getCurrent().getNext());
}
}
public Object getData()
{
return getCurrent().getData();
}
public void insertBeforeCurrentNode(Object bcNode) //beforeCurrentNode
{
Node current;
Node hold;
boolean done;
hold = allocateNode();
hold.setData(bcNode);
current = getListPtr();
done = false;
if (isEmpty())
{
setListPtr(hold);
setCurrent(hold);
}
else if (getCurrent() == getListPtr())
{
System.out.println("hi" + hold);
hold.setNext(getCurrent());
setListPtr(hold);
}
else //if (!isEmpty() && getCurrent() != getListPtr())
{
while (!done && current.getNext() != null)
{
System.out.println("in else if " + hold);
if (current.getNext() == getCurrent())
{
//previous.setNext(hold);
//System.out.println("hi"+ "yo" + " " + getListPtr());
hold.setNext(current.getNext());
current.setNext(hold);
done = true;
}
//previous = current;
current = current.getNext();
}
}
System.out.println(getCurrent());
}
public void insertAfterCurrentNode(Object acNode) //afterCurrentNode
{
Node hold;
hold = allocateNode();
hold.setData(acNode);
if (isEmpty())
{
setListPtr(hold);
setCurrent(hold);
//System.out.println(hold + " hi");
}
else
{
//System.out.println(hold + " hia");
hold.setNext(getCurrent().getNext());
getCurrent().setNext(hold);
}
}
public void insert(Object iNode)
{
insertAfterCurrentNode(iNode);
}
public Object deleteCurrentNode()
{
Object nData;
Node previous;
Node current;
previous = getListPtr();
current = getListPtr();
nData = getCurrent().getData();
if (isEmpty()) {throw new ListEmptyException("The list is currently empty! last()");}
else if (previous == getCurrent())
{
getListPtr().setNext(getCurrent().getNext());
setCurrent(getCurrent().getNext());
nodeCount = nodeCount - 1;
}
else
{
while (previous.getNext() != getCurrent())
{
previous = current;
current = current.getNext();
}
previous.setNext(getCurrent().getNext());
setCurrent(getCurrent().getNext());
nodeCount = nodeCount - 1;
}
return nData;
}
public Object deleteFirstNode(boolean toDelete)
{
if (toDelete)
{
setListPtr(null);
}
return getListPtr();
}
public Object deleteFirstNode()
{
Object deleteFirst;
deleteFirst = deleteFirstNode(true);
return deleteFirst;
}
public int size()
{
return this.nodeCount;
}
public String toString()
{
String nodeString;
Node sNode;
sNode = getCurrent();
//System.out.println(nodeCount);
nodeString = ("List contains " + nodeCount + " nodes");
while (sNode != null)
{
nodeString = nodeString + " " +sNode.getData();
sNode = sNode.getNext();
}
return nodeString;
}
private Node allocateNode()
{
Node newNode;
newNode = new Node();
nodeCount = nodeCount + 1;
return newNode;
}
private void deAllocateNode(Node dNode)
{
dNode.setData(null);
}
private Node getListPtr()
{
return this.firstNode;
}
private void setListPtr(Node pNode)
{
this.firstNode = pNode;
}
private Node getCurrent()
{
return this.currentNode;
}
private void setCurrent(Node cNode)
{
this.currentNode = cNode;
}
private void checkCurrent()
{
if (getCurrent() == null) {throw new InvalidPositionInListException("Current node is null and is set to an invalid position within the list! checkCurrent()");}
}
/**NODE CLASS ----------------------------------------------*/
private class Node
{
private Node next; //serves as a reference to the next node
private Object data;
public Node()
{
this.next = null;
this.data = null;
}
public Object getData()
{
return this.data;
}
public void setData(Object obj)
{
this.data = obj;
}
public Node getNext()
{
return this.next;
}
public void setNext(Node nextNode)
{
this.next = nextNode;
}
public String toString()
{
String nodeString;
Node sNode;
sNode = getCurrent();
//System.out.println(nodeCount);
nodeString = ("List contains " + nodeCount + " nodes");
while (sNode != null)
{
nodeString = nodeString + " " +sNode.getData();
sNode = sNode.getNext();
}
return nodeString;
}
}
}
我让它适合我的 [1] 和 [2] 条件。但我的 [3] (测试 insertBeforeCurrentNode())无法正常工作。我已经设置了打印语句，并且确定我的电流已在某处重置，但我不知道在哪里，可以使用一些指导或解决方案。
[1] 和 [2] 的输出是正确的。 [3] 的输出应为
[3] List contains 26 nodes: z x v t r p n l j h f d b c e g i k m o q s u w y a
感谢您提前提供的任何帮助。
最佳答案
在您的 toString 方法中，您开始打印从 currentNode 到列表末尾的节点。因为您在打印结果之前调用 test.last()，所以 currentNode 将指向列表的最后一个节点，而您的 toString() 只会打印 'a'。
在您的 toString() 方法中，您可能需要更改
sNode = getCurrent();
与
sNode = getListPtr();
打印 26 个节点。
关于java - 链表 - 在当前节点之前插入一个节点，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/8038692/