# 【数据结构】双端链表和双向链表

### 双端链表和双向链表

#### 双端链表:

``````public class Node {
//数据域
public long data;
//指针域
public Node next;
public Node previous;
public Node() {

}

public Node(long data) {
this.data = data;
}

public void display(){
System.out.print(this.data + " ");
}
}
``````

``````public class FirstLastLinkList {
//头结点
private Node first;
//尾结点
private Node last;

first = null;
last = null;
}

/** * 插入一个结点，在头结点后进行插入 */
public void insertFirst(long value) {
Node node = new Node(value);
if(isEmpty()) {
last = node;
}
node.next = first;
first = node;
}

/** * 插入一个结点，从尾结点进行插入 */
public void insertLast(long value) {
Node node = new Node(value);
if(isEmpty()) {
first = node;
} else {
last.next = node;
}
last = node;
}

/** * 删除一个结点，在头结点后进行删除 */
public Node deleteFirst() {
Node tmp = first;
if(first.next == null) {
last = null;
}
first = tmp.next;
return tmp;
}

/** * 显示方法 */
public void display() {
Node current = first;
while(current != null) {
current.display();
current = current.next;
}
System.out.println();
}

/** * 查找方法 */
public Node find(long value) {
Node current = first;
while(current.data != value) {
if(current.next == null) {
return null;
}
current = current.next;
}
return current;
}

/** * 删除方法，根据数据域来进行删除 */
public Node delete(long value) {
Node current = first;
Node previous = first;
while(current.data != value) {
if(current.next == null) {
return null;
}
previous = current;
current = current.next;
}

if(current == first) {
first = first.next;
} else {
previous.next = current.next;
}
return current;

}

/** * 判断是否为空 */
public boolean isEmpty() {
return (first == null);
}
}
``````

#### 双向链表

``````package Study.DataStructure.FirstNodeLast;

/* * 双向链表 */
//头结点
private Node first;
//尾结点
private Node last;

first = null;
last = null;
}

/** * 插入一个结点，在头结点后进行插入 */
public void insertFirst(long value) {
Node node = new Node(value);
if(isEmpty()) {
last = node;
} else {
first.previous = node;
}
node.next = first;
first = node;
}

/** * 插入一个结点，从尾结点进行插入 */
public void insertLast(long value) {
Node node = new Node(value);
if(isEmpty()) {
first = node;
} else {
last.next = node;
node.previous = last;
}
last = node;
}

/** * 删除一个结点，在头结点后进行删除 */
public Node deleteFirst() {
Node tmp = first;
if(first.next == null) {
last = null;
} else {
first.next.previous = null;
}
first = tmp.next;
return tmp;
}

/** * 删除结点，从尾部进行删除 */
public Node deleteLast() {
Node tmp = last;
if(first.next == null) {
first = null;
} else {
last.previous.next = null;
}
last = last.previous;
return last;
}

/** * 显示方法 */
public void display() {
Node current = first;
while(current != null) {
current.display();
current = current.next;
}
System.out.println();
}

/** * 查找方法 */
public Node find(long value) {
Node current = first;
while(current.data != value) {
if(current.next == null) {
return null;
}
current = current.next;
}
return current;
}

/** * 删除方法，根据数据域来进行删除 */
public Node delete(long value) {
Node current = first;
while(current.data != value) {
if(current.next == null) {
return null;
}
current = current.next;
}

if(current == first) {
first = first.next;
} else {
current.previous.next = current.next;
}
return current;

}

/** * 判断是否为空 */
public boolean isEmpty() {
return (first == null);
}
}

``````
原文作者：evan_qb
原文地址: https://blog.csdn.net/Evan_QB/article/details/83964090
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