链表：极简理解和实现

前端

2023-09-11 04:40:17

链表简介

链表是一种线性的数据结构，由一组节点组成，每个节点包含一个数据域和一个指针域，指针域指向下一个节点，形成一个链式结构。

与数组相比，链表具有以下特点：

链表中的元素在内存中不是连续存储的，而是通过指针连接起来的，因此链表可以动态地增长和缩小，而无需移动数据。
链表的插入和删除操作非常简单，只需修改指针即可，而数组则需要移动数据。
链表可以存储任意类型的数据，而数组只能存储相同类型的数据。

链表实现

单向链表

单向链表只允许从一个方向遍历链表，即从头结点开始，沿着指针域指向的下一个节点前进，直到到达尾结点。

class Node {
    int data;
    Node next;

    public Node(int data) {
        this.data = data;
        this.next = null;
    }
}

class SinglyLinkedList {
    private Node head;

    public void addFirst(int data) {
        Node newNode = new Node(data);
        newNode.next = head;
        head = newNode;
    }

    public void addLast(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
            return;
        }
        Node curr = head;
        while (curr.next != null) {
            curr = curr.next;
        }
        curr.next = newNode;
    }

    public int size() {
        int count = 0;
        Node curr = head;
        while (curr != null) {
            count++;
            curr = curr.next;
        }
        return count;
    }

    public boolean isEmpty() {
        return head == null;
    }

    public void printList() {
        Node curr = head;
        while (curr != null) {
            System.out.print(curr.data + " ");
            curr = curr.next;
        }
        System.out.println();
    }

    public void reverseList() {
        Node prev = null;
        Node curr = head;
        Node next = null;
        while (curr != null) {
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        head = prev;
    }
}

双向链表

双向链表允许从两个方向遍历链表，即从头结点开始沿着指针域指向的下一个节点前进，或者从尾结点开始沿着指针域指向的上一个节点后退。

class Node {
    int data;
    Node next;
    Node prev;

    public Node(int data) {
        this.data = data;
        this.next = null;
        this.prev = null;
    }
}

class DoublyLinkedList {
    private Node head;
    private Node tail;

    public void addFirst(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
            tail = newNode;
            return;
        }
        newNode.next = head;
        head.prev = newNode;
        head = newNode;
    }

    public void addLast(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
            tail = newNode;
            return;
        }
        tail.next = newNode;
        newNode.prev = tail;
        tail = newNode;
    }

    public int size() {
        int count = 0;
        Node curr = head;
        while (curr != null) {
            count++;
            curr = curr.next;
        }
        return count;
    }

    public boolean isEmpty() {
        return head == null;
    }

    public void printList() {
        Node curr = head;
        while (curr != null) {
            System.out.print(curr.data + " ");
            curr = curr.next;
        }
        System.out.println();
    }

    public void reverseList() {
        Node prev = null;
        Node curr = head;
        Node next = null;
        while (curr != null) {
            next = curr.next;
            curr.next = prev;
            curr.prev = next;
            prev = curr;
            curr = next;
        }
        head = prev;
        tail = curr;
    }
}