单链表插入、删除和查找操作

一、链表的定义：

链表是一种物理存储结构上非连续存储结构。

二、节点的表示：

节点(Node)==>数据+补充信息

三、单链表的插入：

1、头插法
2、尾插法
3、任意位置插入

class Node{
    public int data;
    public Node next=null;
    Node(int data){
        this.data=data;
    }
}
public class LinkedList {
    private Node head = null;
    //头插法
    public void addFirst(int data) {
        Node node = new Node(data);
        if (head == null) {
            head = node;
            return;
        }
        node.next = head;
        head = node;
    }
    //尾插法
    public void addLast(int data) {
        Node node = new Node(data);
        if (head == null) {
            head = node;
            return;
        }
        Node tail = head;
        while (tail.next != null) {
            tail = tail.next;
        }
        tail.next = node;
    }
        //任意位置插入,第一个数据节点为0号下标
    public boolean addIndex(int index, int data) {
        int size = getSize();
        if (index < 0 || index > size) {
            return false;
        }
        if (index == 0) {
            addFirst(data);
            return true;
        }
        if (index == size) {
            addLast(data);
            return true;
        }
        Node node = new Node(data);
        Node prev = getPos(index - 1);
        node.next = prev.next;
        prev.next = node;
        return true;
    }
        //获得节点总个数
    private int getSize() {
        int size = 0;
        for (Node cur = head; cur != null; cur = cur.next) {
            size++;
        }
        return size;
    }
      // 给定 index 下标, 找到对应的节点
    private Node getPos(int index) {
        Node cur = head;
        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        return cur;
    }
}

四、单链表的删除操作：

1、删除第一次出现关键字为toRemove的节点。
2、删除所有值为toRemoveAll的节点。

class Node{
    public int data;
    public Node next=null;
    Node(int data){
        this.data=data;
    }
}
public class LinkedList {
    private Node head = null;
    //删除第一次出现关键字为toRemove的节点
    public void remove(int toRemove) {
        if (head.data == toRemove) {
            head = head.next;
            return;
        }
        Node prev = searchPrev(toRemove);
        Node toDelete = prev.next;
        prev.next = toDelete.next;
    }
    private Node searchPrev(int toRemove) {
        for (Node cur = head; cur != null && cur.next != null; cur = cur.next) {
            if (cur.next.data == toRemove) {
                return cur;
            }
        }
        return null;
    }
    //删除所有值为toRemoveAll的节点
    public void removeAll(int toRemove) {
        Node prev = head;
        Node cur = head.next;
        while (cur != null) {
            if (cur.data == toRemove) {
                prev.next = cur.next;
                cur = prev.next;
            } else {
                prev = cur;
                cur = cur.next;
            }
        }
        if (head.data == toRemove) {
            head = head.next;
        }
    }
}

五、单链表的查找操作：

查找是否包含关键字toFind是否在单链表中

class Node{
    public int data;
    public Node next=null;
     Node(int data){
     this.data=data;
    }
}
public class LinkedList {
    private Node head = null;
    public boolean contains(int toFind) {
        for (Node cur = head; cur != null; cur = cur.next) {
            if (cur.data == toFind) {
                return true;
            }
        }
        return false;
    }
}

六、单链表清空操作：

class Node{
    public int data;
    public Node next=null;
     Node(int data){
     this.data=data;
    }
}
public class LinkedList {
    private Node head = null;
    public void clear() {
        head = null;
    }
}