【数据结构算法（二）】链表总结

news2024/12/24 11:36:55

🌈键盘敲烂，年薪30万🌈

普通单向链表

双向链表

带哨兵的链表

环形链表

⭐双向带头带环链表的实现⭐

⭐链表基础OJ⭐

普通单向链表

结点结构：只有val 和 next指针

初始时：head = null;

双向链表

指针：prev指针 val next指针

初始时：head = null;

带哨兵的链表

初始时：new 一个新节点sentinel val不重要，next = null

环形链表

尾节点的next指向头结点

初始时：头结点的next指向自己

⭐双向带头带环链表的实现⭐

准备工作

public class TheBestLinkedList implements Iterable<Integer>{

    private Node sentinel = new Node(null, 666, null);

    public TheBestLinkedList() {
        sentinel.prev = sentinel;
        sentinel.next = sentinel;
    }
    private static class Node{
        Node prev;
        int val;
        Node next;

        public Node(Node prev, int val, Node next) {
            this.prev = prev;
            this.val = val;
            this.next = next;
        }
    }
    @Override
    public Iterator<Integer> iterator() {
        return null;
    }
}

addFirst

    public void addFirst(int val){
        Node newNode = new Node(sentinel, val, null);

        Node first = sentinel.next;
        newNode.next = first;
        first.prev = newNode;
        sentinel.next = newNode;
    }

addLast

    public void addLast(int val){
        Node newNode = new Node(null, val, sentinel);
        Node last = sentinel.prev;

        last.next = newNode;
        newNode.prev = last;
        sentinel.prev = newNode;

    }

removedLast

    public Node removedLast(){
        if(isEmpty()){
            return null;
        }
        Node last = sentinel.prev;
        Node removedPrev = last.prev;

        sentinel.prev = removedPrev;
        removedPrev.next = sentinel;
        return last;
    }

removedFirst

    public Node removedFirst(){
        if(isEmpty()){
            return null;
        }
        Node first = sentinel.next;
        // 只有一个节点 removedNext = sentinel
        Node removedNext = first.next;

        sentinel.next = removedNext;
        removedNext.prev = sentinel;
        return first;

    }

isEmpty

    public boolean isEmpty(){
        return sentinel.prev == sentinel;
    }

迭代器遍历

    @Override
    public Iterator<Integer> iterator() {
        return new Iterator<Integer>() {
            Node p = sentinel.next;
            @Override
            public boolean hasNext() {
                return p != sentinel;
            }

            @Override
            public Integer next() {
                int ans =  p.val;
                p = p.next;
                return ans;
            }
        };
    }