Design the realization of the linked list. You can choose to use a singly-linked list or a double-linked list. The nodes in the singly linked list should have two attributes: val and next. val is the value of the current node, and next is a pointer/reference to the next node. If you want to use a doubly linked list, you also need an attribute prev to indicate the previous node in the linked list. Assume that all nodes in the linked list are 0-index.
These functions are implemented in the linked list class:
get(index): Get the value of the index node in the linked list. If the index is invalid, -1 is returned.
addAtHead(val): Add a node with a value of val before the first element of the linked list. After insertion, the new node will become the first node of the linked list.
addAtTail(val): append the node whose value is val to the last element of the linked list.
addAtIndex(index,val): Add a node with value val before the index-th node in the linked list. If index is equal to the length of the linked list, the node will be appended to the end of the linked list. If index is greater than the length of the linked list, no node will be inserted. If the index is less than 0, the node is inserted at the head.
deleteAtIndex(index): If the index index is valid, delete the index node in the linked list.
Example:
MyLinkedList linkedList = new MyLinkedList();
linkedList.addAtHead(1);
linkedList.addAtTail(3);
linkedList.addAtIndex(1,2); //The linked list becomes 1-> 2-> 3
linkedList.get(1); //Return 2
linkedList.deleteAtIndex(1); //Now the linked list is 1-> 3
linkedList.get(1); //Return 3
prompt:
All val values are within [1, 1000].
The number of operations will be within [1, 1000].
Please do not use the built-in LinkedList library.
Source: LeetCode
Link: https://leetcode-cn.com/problems/design-linked-list Click me to jump to the question
/**
* Created with IntelliJ IDEA.
* Description:
* User: starry
* Date: 2021 -01 -25
* Time: 19:56
*/
//节点类
class Node {
public int val;
public Node next;
public Node(){
}
public Node(int val){
this.val = val;
}
}
public class MyLinkedList {
public Node head;//表示当前链表的头
/* public Node createLinked(){
Node node1 = new Node(1);
Node node2 = new Node(2);
Node node3 = new Node(3);
Node node4 = new Node(4);
node1.next = node2;
node2.next = node3;
node3.next = node4;
return node1;
}*/
/** Initialize your data structure here. */
public MyLinkedList() {
// Node node1 = new Node(1);
// Node node2 = new Node(2);
// Node node3 = new Node(3);
// Node node4 = new Node(4);
// node1.next = node2;
// node2.next = node3;
// node3.next = node4;
// head = node1;
}
/** Get the value of the index-th node in the linked list. If the index is invalid, return -1. */
public int get(int index) {
Node cur = head;
int count = 0;
while(cur != null){
if(count == index){
return cur.val;
}
cur = cur.next;
count++;
}
return -1;
}
/** Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list. */
public void addAtHead(int val) {
Node newnode = new Node((val));
newnode.next = head;
head = newnode;
}
/** Append a node of value val to the last element of the linked list. */
public void addAtTail(int val) {
//空链表时，直接将新节点赋给头节点
if(head == null){
head = new Node(val);
return;
}
//非空链表
Node cur = head;
while(cur.next != null){
cur = cur.next;
}
// Node newnode = new Node(val);
// cur.next = newnode;
// newnode.next = null;
cur.next = new Node(val);
cur.next.next = null;
}
/** Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted. */
public void addAtIndex(int index, int val) {
//插在头
if(index == 0){
addAtHead(val);
return;
}
//插在中间
Node cur = new Node();
cur = head;
int count = 0;
while(cur != null){
if(count == index-1){
Node newnode = new Node(val);
if(cur.next == null){
//cur走到了最后一节
cur.next = newnode;
newnode.next = null;
break;
}else{
//cur在中间
Node tmp = cur.next;
cur.next = newnode;
newnode.next = tmp;
}
}
cur = cur.next;
count++;
}
}
/** Delete the index-th node in the linked list, if the index is valid. */
public void deleteAtIndex(int index) {
//删除头节点
if(index == 0){
head = head.next;
return;
}
Node cur = new Node();
cur = head;
int count = 0;
while(cur.next != null){
if(count == index-1){
if(cur.next.next == null){
//删除尾节点
cur.next = null;
}else{
//删除中间节点
cur.next = cur.next.next;
}
break;
}
cur = cur.next;
count++;
}
}
public static void main(String[] args) {
MyLinkedList myLinkedList = new MyLinkedList();
// Node head = myLinkedList.createLinked();
// System.out.println("======================");
// System.out.println(myLinkedList.get(1));
// myLinkedList.addAtHead(0);
// myLinkedList.addAtTail(5);
// myLinkedList.addAtIndex(2,0);
// myLinkedList.deleteAtIndex(4);
myLinkedList.addAtHead(1);
myLinkedList.addAtTail(3);
myLinkedList.addAtIndex(2,2);
// System.out.println(myLinkedList.get(1));
// myLinkedList.deleteAtIndex(1);
// System.out.println(myLinkedList.get(1));
Node cur = myLinkedList.head;
while(cur != null){
System.out.println(cur.val);
cur = cur.next;
}
}
}
/**
* 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);
*/