Examples of Java simulation of singly linked list and double-ended linked list data structures-javaTutorial-php.cn

Simulate singly linked list

Linear table:
Linear table (also called sequence table) is the most basic, simplest, and most commonly used data structure.
The relationship between data elements in a linear table is a one-to-one relationship, that is, except for the first and last data elements, other data elements are connected end to end.
The linear table has a simple logical structure and is easy to implement and operate.
In practical applications, linear tables are used in the form of special linear tables such as stacks, queues, and strings.
The basic characteristics of linear structure are:
1. There must be only one "first element" in the set;
2. There must be only one "last element" in the set;
3. Except for the last element, all elements have a unique successor (successor);
4. Except for the first element, all elements have a unique precursor (antecedent).

Linked list: linked list
A linked list is a non-continuous, non-sequential storage structure on a physical storage unit. The logical order of data elements is realized through the pointer link order in the linked list
Each Data items are contained in "Links".
The link point is an object of a class, which can be called Link. There are many similar link points in the linked list, and each Link contains a field next that refers to the next link point.
The linked list object itself saves a reference to the first link point first. (If there is no first, it cannot be positioned)
The linked list cannot directly access the data items like the array (using subscripts), but needs to use the relationship between the data to locate, that is, access the next link referenced by the link point. Click, and then the next one, until the required data is accessed
The time complexity of inserting and deleting at the chain head is O(1), because you only need to change the pointer of the reference
And search and delete the specified result point, inserting after the specified node, these operations require searching half of the nodes in the linked list on average, and the efficiency is O(N).
Singly linked list:
Representing a linear list as a "sequence of nodes" is called a linear linked list (singly linked list)
It is a chained access data structure, which is stored in a set of storage units with arbitrary addresses. Data elements in a linear table. (This group of storage units can be either continuous or discontinuous)
Structure of link points:

Examples of Java simulation of singly linked list and double-ended linked list data structures

Data field data that stores node values ;The pointer field (chain field) that stores the reference of the node next
The linked list links the n nodes of the linear list together in their logical order through the link field of each node.
A linked list with only one link domain for each node is called a Single Linked List. In one direction, there are only references to subsequent nodes

/** 
 * 单链表:头插法 后进先出 
 * 将链表的左边称为链头，右边称为链尾。 
 * 头插法建单链表是将链表右端看成固定的，链表不断向左延伸而得到的。 
 * 头插法最先得到的是尾结点 
 * @author stone 
 */
public class SingleLinkedList<T> { 
    
  private Link<T> first;    //首结点 
  public SingleLinkedList() { 
      
  } 
    
  public boolean isEmpty() { 
    return first == null; 
  } 
    
  public void insertFirst(T data) {// 插入 到 链头 
    Link<T> newLink = new Link<T>(data); 
    newLink.next = first; //新结点的next指向上一结点 
    first = newLink; 
  } 
    
  public Link<T> deleteFirst() {//删除 链头 
    Link<T> temp = first; 
    first = first.next; //变更首结点，为下一结点 
    return temp; 
  } 
    
  public Link<T> find(T t) { 
    Link<T> find = first; 
    while (find != null) { 
      if (!find.data.equals(t)) { 
        find = find.next; 
      } else { 
        break; 
      } 
    } 
    return find; 
  } 
    
  public Link<T> delete(T t) { 
    if (isEmpty()) { 
      return null; 
    } else { 
      if (first.data.equals(t)) { 
        Link<T> temp = first; 
        first = first.next; //变更首结点，为下一结点 
        return temp; 
      } 
    } 
    Link<T> p = first; 
    Link<T> q = first; 
    while (!p.data.equals(t)) { 
      if (p.next == null) {//表示到链尾还没找到 
        return null; 
      } else { 
        q = p; 
        p = p.next; 
      } 
    } 
      
    q.next = p.next; 
    return p; 
  } 
    
  public void displayList() {//遍历 
    System.out.println("List (first-->last):"); 
    Link<T> current = first; 
    while (current != null) { 
      current.displayLink(); 
      current = current.next; 
    } 
  } 
    
  public void displayListReverse() {//反序遍历 
    Link<T> p = first, q = first.next, t; 
    while (q != null) {//指针反向，遍历的数据顺序向后 
      t = q.next; //no3 
      if (p == first) {// 当为原来的头时，头的.next应该置空 
        p.next = null; 
      } 
      q.next = p;// no3 -> no1 pointer reverse 
      p = q; //start is reverse 
      q = t; //no3 start 
    } 
    //上面循环中的if里，把first.next 置空了, 而当q为null不执行循环时，p就为原来的最且一个数据项，反转后把p赋给first 
    first = p;  
    displayList(); 
  } 
    
  class Link<T> {//链结点 
    T data;   //数据域 
    Link<T> next; //后继指针，结点    链域 
    Link(T data) { 
      this.data = data; 
    } 
    void displayLink() { 
      System.out.println("the data is " + data.toString()); 
    } 
  } 
    
  public static void main(String[] args) { 
    SingleLinkedList<Integer> list = new SingleLinkedList<Integer>(); 
    list.insertFirst(33); 
    list.insertFirst(78); 
    list.insertFirst(24); 
    list.insertFirst(22); 
    list.insertFirst(56); 
    list.displayList(); 
      
    list.deleteFirst(); 
    list.displayList(); 
      
    System.out.println("find:" + list.find(56)); 
    System.out.println("find:" + list.find(33)); 
      
    System.out.println("delete find:" + list.delete(99)); 
    System.out.println("delete find:" + list.delete(24)); 
    list.displayList(); 
    System.out.println("----reverse----"); 
    list.displayListReverse(); 
  } 
}

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List (first-->last):
the data is 56
the data is 22
the data is 24
the data is 78
the data is 33
List (first-->last):
the data is 22
the data is 24
the data is 78
the data is 33
find:null
find:linked_list.SingleLinkedList$Link@4b71bbc9
delete find:null
delete find:linked_list.SingleLinkedList$Link@17dfafd1
List (first-->last):
the data is 22
the data is 78
the data is 33
----reverse----
List (first-->last):
the data is 33
the data is 78
the data is 22

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Singly linked list: tail insertion method, last in first out - If the left end of the linked list is fixed and the linked list continues to extend to the right, this method of establishing a linked list is called tail insertion method.
When the tail insertion method creates a linked list, the head pointer is fixed, so a tail pointer must be set up to extend to the right side of the linked list.
The tail insertion method first obtains the head node.

public class SingleLinkedList2<T> {
    
  private Link<T> head;   //首结点
  public SingleLinkedList2() {
      
  }
    
  public boolean isEmpty() {
    return head == null;
  }
    
  public void insertLast(T data) {//在链尾 插入
    Link<T> newLink = new Link<T>(data);
    if (head != null) {
      Link<T> nextP = head.next;
      if (nextP == null) {
        head.next = newLink;
      } else {
        Link<T> rear = null;
        while (nextP != null) {
          rear = nextP;
          nextP = nextP.next;
        }
        rear.next = newLink;
      }
    } else {
      head = newLink;
    }
  }
    
  public Link<T> deleteLast() {//删除 链尾
    Link<T> p = head;
    Link<T> q = head;
    while (p.next != null) {// p的下一个结点不为空，q等于当前的p(即q是上一个，p是下一个) 循环结束时，q等于链尾倒数第二个
      q = p;
      p = p.next;
    }
    //delete
    q.next = null;
    return p;
  }
    
  public Link<T> find(T t) {
    Link<T> find = head;
    while (find != null) {
      if (!find.data.equals(t)) {
        find = find.next;
      } else {
        break;
      }
    }
    return find;
  }
    
  public Link<T> delete(T t) {
    if (isEmpty()) {
      return null;
    } else {
      if (head.data.equals(t)) {
        Link<T> temp = head;
        head = head.next; //变更首结点，为下一结点
        return temp;
      }
    }
    Link<T> p = head;
    Link<T> q = head;
    while (!p.data.equals(t)) {
      if (p.next == null) {//表示到链尾还没找到
        return null;
      } else {
        q = p;
        p = p.next;
      }
    }
      
    q.next = p.next;
    return p;
  }
    
  public void displayList() {//遍历
    System.out.println("List (head-->last):");
    Link<T> current = head;
    while (current != null) {
      current.displayLink();
      current = current.next;
    }
  }
    
  public void displayListReverse() {//反序遍历
    Link<T> p = head, q = head.next, t;
    while (q != null) {//指针反向，遍历的数据顺序向后
      t = q.next; //no3
      if (p == head) {// 当为原来的头时，头的.next应该置空
        p.next = null;
      }
      q.next = p;// no3 -> no1 pointer reverse
      p = q; //start is reverse
      q = t; //no3 start
    }
    //上面循环中的if里，把head.next 置空了, 而当q为null不执行循环时，p就为原来的最且一个数据项，反转后把p赋给head
    head = p; 
    displayList();
  }
    
  class Link<T> {//链结点
    T data;   //数据域
    Link<T> next; //后继指针，结点    链域
    Link(T data) {
      this.data = data;
    }
    void displayLink() {
      System.out.println("the data is " + data.toString());
    }
  }
    
  public static void main(String[] args) {
    SingleLinkedList2<Integer> list = new SingleLinkedList2<Integer>();
    list.insertLast(33);
    list.insertLast(78);
    list.insertLast(24);
    list.insertLast(22);
    list.insertLast(56);
    list.displayList();
      
    list.deleteLast();
    list.displayList();
      
    System.out.println("find:" + list.find(56));
    System.out.println("find:" + list.find(33));
      
    System.out.println("delete find:" + list.delete(99));
    System.out.println("delete find:" + list.delete(78));
    list.displayList();
    System.out.println("----reverse----");
    list.displayListReverse();
  }
}

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List (head-->last):
the data is 33
the data is 78
the data is 24
the data is 22
the data is 56
List (head-->last):
the data is 33
the data is 78
the data is 24
the data is 22
find:null
find:linked_list.SingleLinkedList2$Link@4b71bbc9
delete find:null
delete find:linked_list.SingleLinkedList2$Link@17dfafd1
List (head-->last):
the data is 33
the data is 24
the data is 22
----reverse----
List (head-->last):
the data is 22
the data is 24
the data is 33

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Simulate a double-ended linked list and use linked lists to implement stacks and queues
Double-ended linked list:
A double-ended linked list is very similar to a traditional linked list. It just adds a new attribute - the reference to the last link point rear
This will make it very easy to insert at the end of the chain. Just change rear's next to the new node, instead of looping to search the last node
So when there are insertFirst and insertLast
to delete the link head, you only need to change the reference point; delete the link At the end, the next of the penultimate node needs to be left blank,
and there is no reference pointing to it, so a loop is still needed to read the operation

/**
 * 双端链表
 * @author stone
 */
public class TwoEndpointList<T> {
  private Link<T> head;   //首结点
  private Link<T> rear;   //尾部指针
    
  public TwoEndpointList() {
      
  }
    
  public T peekHead() {
    if (head != null) {
      return head.data;
    }
    return null;
  }
    
  public boolean isEmpty() {
    return head == null;
  }
    
  public void insertFirst(T data) {// 插入 到 链头
    Link<T> newLink = new Link<T>(data);
    newLink.next = head; //新结点的next指向上一结点
    head = newLink;
  }
    
  public void insertLast(T data) {//在链尾 插入
    Link<T> newLink = new Link<T>(data);
    if (head == null) {
      rear = null;
    }
    if (rear != null) {
      rear.next = newLink;
    } else {
      head = newLink;
      head.next = rear;
    }
    rear = newLink; //下次插入时，从rear处插入
      
  }
    
  public T deleteHead() {//删除 链头
    if (isEmpty()) return null;
    Link<T> temp = head;
    head = head.next; //变更首结点，为下一结点
    if (head == null) {
    <span style="white-space:pre">  </span>rear = head;
    }
    return temp.data;
  }
    
  public T find(T t) {
    if (isEmpty()) {
      return null;
    }
    Link<T> find = head;
    while (find != null) {
      if (!find.data.equals(t)) {
        find = find.next;
      } else {
        break;
      }
    }
    if (find == null) {
      return null;
    }
    return find.data;
  }
    
  public T delete(T t) {
    if (isEmpty()) {
      return null;
    } else {
      if (head.data.equals(t)) {
        Link<T> temp = head;
        head = head.next; //变更首结点，为下一结点
        return temp.data;
      }
    }
    Link<T> p = head;
    Link<T> q = head;
    while (!p.data.equals(t)) {
      if (p.next == null) {//表示到链尾还没找到
        return null;
      } else {
        q = p;
        p = p.next;
      }
    }
    q.next = p.next;
    return p.data;
  }
    
  public void displayList() {//遍历
    System.out.println("List (head-->last):");
    Link<T> current = head;
    while (current != null) {
      current.displayLink();
      current = current.next;
    }
  }
    
  public void displayListReverse() {//反序遍历
    if (isEmpty()) {
      return;
    }
    Link<T> p = head, q = head.next, t;
    while (q != null) {//指针反向，遍历的数据顺序向后
      t = q.next; //no3
      if (p == head) {// 当为原来的头时，头的.next应该置空
        p.next = null;
      }
      q.next = p;// no3 -> no1 pointer reverse
      p = q; //start is reverse
      q = t; //no3 start
    }
    //上面循环中的if里，把head.next 置空了, 而当q为null不执行循环时，p就为原来的最且一个数据项，反转后把p赋给head
    head = p; 
    displayList();
  }
    
  class Link<T> {//链结点
    T data;   //数据域
    Link<T> next; //后继指针，结点    链域
    Link(T data) {
      this.data = data;
    }
    void displayLink() {
      System.out.println("the data is " + data.toString());
    }
  }
    
  public static void main(String[] args) {
    TwoEndpointList<Integer> list = new TwoEndpointList<Integer>();
    list.insertLast(1);
    list.insertFirst(2);
    list.insertLast(3);
    list.insertFirst(4);
    list.insertLast(5);
    list.displayList();
      
    list.deleteHead();
    list.displayList();
      
    System.out.println("find:" + list.find(6));
    System.out.println("find:" + list.find(3));
  
    System.out.println("delete find:" + list.delete(6));
    System.out.println("delete find:" + list.delete(5));
    list.displayList();
    System.out.println("----reverse----");
    list.displayListReverse();
  }
}

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List (head-->last):
the data is 4
the data is 2
the data is 1
the data is 3
the data is 5
List (head-->last):
the data is 2
the data is 1
the data is 3
the data is 5
find:null
find:3
delete find:null
delete find:5
List (head-->last):
the data is 2
the data is 1
the data is 3
----reverse----
List (head-->last):
the data is 3
the data is 1
the data is 2

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Use a linked list to implement the stack, which can be achieved by inserting forward a single linked list.
This class uses a double-ended linked list to implement:

public class LinkStack<T> {
  private TwoEndpointList<T> datas;
    
  public LinkStack() {
    datas = new TwoEndpointList<T>();
  }
    
  // 入栈
  public void push(T data) {
    datas.insertFirst(data);
  }
    
  // 出栈
  public T pop() {
    return datas.deleteHead();
  }
    
  // 查看栈顶
  public T peek() {
    return datas.peekHead();
  }
    
  //栈是否为空
  public boolean isEmpty() {
    return datas.isEmpty();
  }
    
  public static void main(String[] args) {
    LinkStack<Integer> stack = new LinkStack<Integer>();
    for (int i = 0; i < 5; i++) {
      stack.push(i);
    }
    for (int i = 0; i < 5; i++) {
      Integer peek = stack.peek();
      System.out.println("peek:" + peek);
    }
    for (int i = 0; i < 6; i++) {
      Integer pop = stack.pop();
      System.out.println("pop:" + pop);
    }
      
    System.out.println("----");
    for (int i = 5; i > 0; i--) {
      stack.push(i);
    }
    for (int i = 5; i > 0; i--) {
      Integer peek = stack.peek();
      System.out.println("peek:" + peek);
    }
    for (int i = 5; i > 0; i--) {
      Integer pop = stack.pop();
      System.out.println("pop:" + pop);
    }
  }
}

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peek:4
peek:4
peek:4
peek:4
peek:4
pop:4
pop:3
pop:2
pop:1
pop:0
pop:null
----
peek:1
peek:1
peek:1
peek:1
peek:1
pop:1
pop:2
pop:3
pop:4
pop:5

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Linked list implementation queue Implementation using double-ended linked list:

public class LinkQueue<T> {
  private TwoEndpointList<T> list;
    
  public LinkQueue() {
    list = new TwoEndpointList<T>();
  }
  //插入队尾
  public void insert(T data) {
    list.insertLast(data);
  }
  //移除队头
  public T remove() {
    return list.deleteHead();
  }
  //查看队头
  public T peek() {
    return list.peekHead();
  }
    
  public boolean isEmpty() {
    return list.isEmpty();
  }
    
  public static void main(String[] args) {
    LinkQueue<Integer> queue = new LinkQueue<Integer>();
    for (int i = 1; i < 5; i++) {
      queue.insert(i);
    }
    for (int i = 1; i < 5; i++) {
      Integer peek = queue.peek();
      System.out.println("peek:" + peek);
    }
    for (int i = 1; i < 5; i++) {
      Integer remove = queue.remove();
      System.out.println("remove:" + remove);
    }
      
    System.out.println("----");
      
    for (int i = 5; i > 0; i--) {
      queue.insert(i);
    }
    for (int i = 5; i > 0; i--) {
      Integer peek = queue.peek();
      System.out.println("peek2:" + peek);
    }
    for (int i = 5; i > 0; i--) {
      Integer remove = queue.remove();
      System.out.println("remove:" + remove);
    }
  }
}

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peek:1
peek:1
peek:1
peek:1
remove:1
remove:2
remove:3
remove:4
----
peek2:5
peek2:5
peek2:5
peek2:5
peek2:5
remove:5
remove:4
remove:3
remove:2
remove:1

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