لیست پیوندی Leetcode Day3 – انجمن DEV

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */

        while(head!=null){
            if(head.val == val){
                head = head.next;
            }

        }
        ListNode preNode = head;
        ListNode curNode = head;

        while(curNode != null){
                            System.out.println("find");
            if(curNode.val == val){
                preNode.next = curNode.next;
            }else{
                preNode = curNode;
            }
            curNode = curNode.next;
        }
        return head;  

    public ListNode removeElements(ListNode head, int val) {
        ListNode preNode = head;
        ListNode curNode = head;


        while(curNode != null){
            if(curNode.val == val){
                // head is different from other element because it is an entry of the Linked list
                if(curNode == head){
                    head = head.next;
                    curNode = head;
                    preNode = head;
                }else{
                    // if the node is normal node we just do the remove 
                    preNode.next = curNode.next;
                }
            }else{
                preNode = curNode;
            }

            curNode = curNode.next;
        }
        return head;  
    }

    public ListNode removeElements(ListNode head, int val) {

        while((head != null) && (head.val == val)){
            head = head.next;
        }

        ListNode preNode = head;
        ListNode curNode = head;

        while(curNode!=null){
            if(curNode.val == val){
                preNode.next = curNode.next;
            }else{
                preNode = curNode;
            }
            curNode = curNode.next;
        }
        return head;
    }

class MyLinkedList {

    public Node head;
    public Node tail;
    public int size;


    public class Node{
        public int val;
        public Node next;

        public Node(){
        }
        public Node(int val){
            this.val = val;
        }
        public Node(int val, Node next){
            this.val = val;
            this.next = next;
        }
    }

    public MyLinkedList() {
        size = 0;
        head = null;
        tail = null;
    }

    public int get(int index) {
        int count = 0;
        Node cur = head;
        while(cur != null){
            if(count == index){
                return cur.val;
            }
            cur = cur.next;
            count ++;
        }
        return -1;
    }

    public void addAtHead(int val) {
        if(head==null){
            head = new Node(val);
            // if head == null means this list is empty
            tail = head;
        }        
        else{
            Node temp = head;
            head = new Node(val);
            head.next = temp;
        }
        size++;
    }

    public void addAtTail(int val) {
        if(tail==null){
            tail = new Node(val);
            head = tail;
        }
        else{
            Node temp = tail;
            temp.next = new Node(val);
            tail = temp.next;
        }  
        size++;  
    }

    public void addAtIndex(int index, int val) {
        if(index > size){
            return;
        }

        if(index == 0){
            addAtHead(val);
        }
        if(index == size){
            addAtTail(val);
        }

        else{
            int count = 0;
            Node pre = head;
            Node cur = head;
            while(cur != null){
                if(count == index){
                    Node insert = new Node(val);
                    pre.next = insert;
                    // important
                    insert.next = cur;
                    size++;
                    return;
                }
                else{
                    pre = cur;
                    cur = cur.next;
                    count ++;
                }
            }
        } 
    }

    public void deleteAtIndex(int index) {
        if(index > size){
            return;
        }

        if(index == 0){
            if(head!=null){
                head = head.next;
                if(head == null){
                    tail = null;
                }
                size--;
                return;
            }
        }else{
            int count = 0;
            Node pre = head;
            Node cur = head;
            while(cur != null){
                if(count == index){
                    pre.next = cur.next;
                    if(pre.next == null){
                        tail = pre;
                    }
                    size--;
                    return;
                }
                pre = cur;
                cur = cur.next;
                count++;
            }

        }
    }
}

/**
 * Your MyLinkedList object will be instantiated and called as such:
 * MyLinkedList obj = new MyLinkedList();
 * int param_1 = obj.get(index);
 * obj.addAtHead(val);
 * obj.addAtTail(val);
 * obj.addAtIndex(index,val);
 * obj.deleteAtIndex(index);
 */