java——单链表方法实现

╰+攻爆jí腚メ 2022-10-29 09:06 159阅读 0赞

/**
     * 单链表
     */
    class Node{
        
        public int data;
        public Node next;
        public Node(int data){
        
            this.data = data;
            this.next = null;
        }
    }
    
    public class MyLinkedList {
        
        public Node head;//保存头节点的引用
    
        // 1、无头单向非循环链表实现---------------------------------------------------------
        //头插法
        public void addFirst(int data){
        
            Node node = new Node(data);//有了一个节点
            if (this.head == null){
        
                //第一次插入节点
                this.head = node;
                return;
            }
            node.next = this.head;
            this.head = node;
        }
    
        //尾插法
        public void addLast(int data){
        
            Node node = new Node(data);
            Node cur = this.head;
            if (cur == null){
        
                this.head = node;
                return;
            }
            while (cur.next != null){
        
                cur = cur.next;
            }
            cur.next = node;
        }
    
        //2.任意位置插入,第一个数据节点为0号下标-------------------------------------------------
        public void addIndex(int index,int data){
        
            Node node = new Node(data);
            if (index == 0){
        
                addFirst(data);
                return ;
            }
            if (index == this.size()){
        
                addLast(data);
                return;
            }
            Node cur = searchIndex(index);
            node.next = cur.next;
            cur.next = node;
        }
        private Node searchIndex(int index){
        
            if (index < 0 || index > this.size()){
        
                throw new RuntimeException("index位置不合法");
            }
            Node cur = this.head;
            while (index - 1 != 0){
        
                cur = cur.next;
                index--;
            }
            return cur;
        }
    
        //查找是否包含关键字key是否在单链表当中-------------------------------------------------------
        public boolean contains(int key){
        
            Node cur = this.head;
            while (cur != null){
        
                if (cur.data == key){
        
                    return true;
                }
                cur = cur.next;
            }
            return false;
        }
    
        //删除第一次出现关键字为key的节点------------------------------------------------------------
        public void remove(int key){
        
            if (this.head == null){
        
                return;
            }
            //如果是头节点，直接删除
            if (this.head.data == key){
        
                this.head = this.head.next;
            }
            Node prev = findPast(key);
            if (prev == null){
        
                System.out.println("没有这个节点");
            }
            Node del = prev.next;
            prev.next = del.next;
        }
        //找目标节点的前一个节点
        public Node findPast(int key){
        
            Node prev = this.head;
            while (prev.next != null){
        
                if(prev.next.data == key){
        
                    return prev;
                }
            }
            return null;
        }
    
        //删除所有值为key的节点------------------------------------------------------------------
        public void removeAllKey(int key){
        
            Node prev = this.head;
            Node cur = prev.next;
            while (cur != null){
        
                if (cur.data == key){
        
                    prev.next = cur.next;
                    cur = cur.next;
                }else {
        
                    prev = cur;
                    cur = cur.next;
                }
            }
            //如果刚开始的头节点重复了，就删除头节点
            if (this.head.data == key){
        
                this.head = this.head.next;
            }
        }
    
    
        //得到单链表的长度-------------------------------------------------------------------
        public int size(){
        
            int count = 0;
            Node cur = this.head;
            while (cur != null){
        
                count++;
                cur = cur.next;
            }
            return count;
        }
    
        //打印------------------------------------------------------------------------------
        public void display(){
        
            Node cur = this.head;
            while (cur != null){
        
                System.out.print(cur.data + " ");
                cur  = cur.next;
            }
        }
    
        public void clear(){
        
            this.head = null;
        }
    }

主函数

public static void main(String[] args) {
        
            MyArrayList myArrayList = new MyArrayList();
            myArrayList.add(0,0);
            myArrayList.add(1,1);
            myArrayList.add(2,2);
            myArrayList.add(3,3);
            myArrayList.add(4,4);
            myArrayList.add(5,5);
            myArrayList.add(6,6);
    //        也可以这样赋值：
    //        for (int i = 0; i < 10; i++){
        
    //            myArrayList.add(i, i);
    //        }
            myArrayList.add(7,19);
            myArrayList.display();
    
            System.out.println(myArrayList.search(19));
    
            System.out.println(myArrayList.getPos(5));
    
            myArrayList.setPos(2,64);
            myArrayList.display();
    
        }

## 相关练习题如下 ##

class ListNode {
        
        public int val;
        public ListNode next;
        public ListNode(int val){
        
            this.val = val;
            this.next = null;
        }
    }
    
    public class TestDemo1025_1 {
        
        public ListNode head;
    
        //给定一个头结点为 head 的非空单链表，返回链表的中间结点。
    //
    //如果有两个中间结点，则返回第二个中间结点。
    //
    //
        public ListNode middleNode() {
        
            ListNode fast = this.head;
            ListNode slow = this.head;
            while (fast != null && fast.next != null){
        
                fast = fast.next.next;
                slow = slow.next;
            }
            return slow;
        }
    
    
        //链表中倒数第k个节点
        public ListNode findLastK(int k){
        
            if (k <= 0 ){
        
                System.out.println("不合法");
                return null;
            }
            ListNode fast = this.head;
            ListNode slow = this.head;
            while (k-1 != 0){
        
                if (fast.next != null){
        
                    fast = fast.next;
                    k--;
                }else {
        
                    System.out.println("没有这个节点");
                    return null;
                }
            }
            while (fast.next != null){
        
                slow = slow.next;
                fast = fast.next;
            }
            return slow;
        }
    
        //现有一链表的头指针 ListNode* pHead，给一定值x，
        // 编写一段代码将所有小于x的结点排在其余结点之前，且不能改变原来的数据顺序，返回重新排列后的链表的头指针。
        public ListNode partition(int x){
        
            ListNode bs = null;
            ListNode be = null;
            ListNode as = null;
            ListNode ae = null;
            ListNode cur = this.head;
            while (cur != null) {
        
                if (cur.val < x){
        
                    //第一次插入
                    if (bs == null){
        
                        bs = cur;
                        be = bs;
                    }else {
        
                        be.next = cur;
                        be = be.next;
                    }
                }else {
        
                    //第一次插入
                    if (as == null){
        
                        as = cur;
                        ae = as;
                    }else {
        
                        ae.next = cur;
                        ae = ae.next;
                    }
                }
                cur = cur.next;
            }
            //1.判断bs是否为空，如果为空，返回as
            if (bs == null){
        
                return as;
            }
            //2.如果bs不为空，需要进行拼接
            be.next = as;
            //3.如果ae不为空，则需要吧ae.next置为空
            if (ae != null){
        
                ae.next = null;
            }
            return bs;
        }
    
        //在一个排序的链表中，存在重复的结点，请删除该链表中重复的结点，重复的结点不保留，返回链表头指针。
        // 例如，链表1->2->3->3->4->4->5 处理后为 1->2->5
        public ListNode deleteDuplication(ListNode pHead) {
        
            ListNode cur = this.head;
            ListNode newHead = new ListNode(-1);
            ListNode tmp = newHead;
            while (cur != null){
        
                if (cur.next != null && cur.val == cur.next.val){
        
                    while (cur.next != null && cur.val == cur.next.val){
        
                        cur = cur.next;
                    }
                    cur = cur.next;
                }else {
        
                    tmp.next = cur;
                    tmp = tmp.next;
                    cur = cur.next;
                }
            }
            tmp.next = null;
            return newHead.next;
        }
        //反转单链表
        public ListNode change(){
        
            ListNode prev = null;
            ListNode cur = this.head;
            ListNode curNext = null;
            ListNode newHead = null;
    
            while (cur != null){
        
                curNext = cur.next;
                if (curNext == null){
        
                    newHead = cur;
                }
                cur.next = prev;
                prev = cur;
                cur = curNext;
            }
            return newHead;
        }
    
    
        //对于一个链表，请设计一个时间复杂度为O(n),额外空间复杂度为O(1)的算法，判断其是否为回文结构。
        //
        //给定一个链表的头指针A，请返回一个bool值，代表其是否为回文结构。保证链表长度小于等于900。
        //
        //测试样例：
        //1->2->2->1
        //返回：true
        public boolean chkPalindrome() {
        
            // write code here
            ListNode fast = this.head;
            ListNode slow = this.head;
    
            if (this.head == null){
        
                return false;
            }
            if (this.head.next == null){
        
                //只有头节点自己，必然是回文
                return true;
            }
            //找到中间
            while (fast != null && fast.next != null){
        
                fast = fast.next.next;
                slow = slow.next;
            }
            //反转后半段
            ListNode cur =slow.next;
            while (cur != null){
        
                ListNode curNext = cur.next;
                cur.next = slow;
                slow = cur;
                cur = curNext.next;
            }
            //此时slow是最后一个了
            while (slow != this.head){
        
                if (this.head.val != slow.val){
        
                    return false;
                }
                if (this.head.next == slow){
        
                    return true;
                }
                slow = slow.next;
                this.head = this.head.next;
            }
            return true;
        }
        
    }