在链表中的特定位置插入节点答案

【问题标题】：Inserting a node at a specific position in a Linked list在链表中的特定位置插入节点
【发布时间】：2017-03-07 05:17:06
【问题描述】：

给我一个指向链表头节点的指针，一个要添加到链表中的整数以及必须插入该整数的位置。将此节点插入所需位置后，我需要返回头节点。

我编写的代码由于某种原因无法运行并进入无限循环。

  class Node {
     int data;
     Node next;
  }


Node InsertNth(Node head, int data, int position) {
    int count = 0;
    Node node = head;
    Node prev = null;
    while(count != position){
      count++;
      node = node.next;
      prev = node;
    }

    Node newNode = new Node();
    newNode.data = data;


    newNode.next = node;
    if(count == 0){
          head = newNode;
       }else{
          prev.next = newNode;
    }

    return head;          
}

【问题讨论】：

提示：在while 循环结束后放置：System.out.println("node = " + node.data + " prev = " + prev.data); 实际上，您需要先确保node 和prev 不为空。但我认为如果你这样做，你将能够发现错误。

标签： java algorithm data-structures linked-list

【解决方案1】：

node = node.next;
prev = node;

这应该是相反的顺序

prev = node;
node = node.next;

而且代码在很多情况下也没有检查，例如指定的位置是否大于链表的大小。尝试重写代码，您能否提及您用于测试功能的值。我认为prev=node 应该抛出异常，因为 prev 没有初始化

【讨论】：

【解决方案2】：

首先，我找到了位置。然后通过更改指针在该位置插入新节点。

  Node InsertNth(Node head, int data, int position) {

    Node newNode= new Node();
    newNode.data=data;

    Node ptr = head;
    pos = pos - 1;
    for (int i = 1; ; i++) {
     if(ptr==null)
       {  break;
           }
        if (i == pos) {
            newNode.next=ptr.next;
            ptr.next=newNode;
            break;
        }
        ptr = ptr.next;
    }
}

【讨论】：

【解决方案3】：

public static Node InsertNth(Node head, int data, int position) {

          Node node = new Node(data);
          node.next = null;
          if (head == null && position == 0){
              head = node;
          }
          else if(head != null && position == 0){
              node.next = head;
              head = node;
          }
          Node tempCurrentNode = head ;
          Node tempPreviousNode = null;
          int index = 0;
          while (index < position) {
              tempPreviousNode =  tempCurrentNode;
              tempCurrentNode = tempCurrentNode.next;
              index = index + 1;
          }
            node.next = tempCurrentNode;
            tempPreviousNode.next = node;

         return head;
    }

【讨论】：

【解决方案4】：

var head;

class Node{
    constructor(val) {
        this.data=val;
        this.next=null;
    }
}

const sortedAdd = val => {
    new_node = new Node(val);
    var current
    if(head == null || head.data > new_node.data) {
        new_node.next = head;
        head = new_node;
    } else {
        current = head;
        while (current.next != null && current.next.data < new_node.data) {
            current = current.next;
        }
        new_node.next = current.next;
        current.next = new_node;

    }
}

const add = val => {
    new_node = new Node(val);
    var current
    if(head == null) {
        head = new_node;
    } else {
        current = head;
        while (current.next != null ) {
            current = current.next;
        }
        current.next = new_node;

    }
}

const insertAtPos= (val, insertIndex) => {
    new_node = new Node(val);
    var current, prev;
    if(head == null) {
        head = new_node;
    } else {
        current = head;
        let index=0;
        prev =current;

        while (index <= insertIndex) {
            if(0 === insertIndex) {
                new_node.next = current;
                prev.next = new_node;
                break;  
            } else if(index === insertIndex) {
                new_node.next = current;
                prev.next = new_node;
                break;
            } 
            
            prev = current;
            current = current.next;
            index++;
        }
    }
}
const deleteNode = val =>{
    var current = head;
    var prev;
    while(current != null) {
        if(current.data === val) {
            console.log('Deleted node ', current.data);
            prev.next = current.next;
        }
        prev = current;
        current = current.next;
    }
}
const printList = () => {
    let temp = head;
    while(temp != null) {
        console.log(temp.data);
        temp = temp.next;
    }
}

[5, 10, 7, 3, 1, 9].map(d => add(d));
console.log('Before');
printList();
console.log('After ');
insertAtPos(4, 3);
// deleteNode(3);
printList();

//output

之前 5 10 7 3 1 9 后 5 10 7 4 3 1 9

【讨论】：