Question

                   // ConsoleApplication1.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
using namespace std;

struct Node {
    int data;
    Node* next; 
};
Node* head = NULL;
int size;
Node* tail = NULL;

void printLinkedList() {
    Node *search = head;
    if (head == NULL) {
        cout << "linkedlist is empty" << endl;
    }
    else { 
        while (search != NULL){
            cout << search->data << endl;
            search = search->next;
        }
    }
}
int sizeLinkedList() {
    size = 1;
    Node* current = head;
    while (current->next != NULL) {
        current = current->next;
        size = size + 1;
        }
    cout << size << endl;
    return size;
}

Node *getNode(int position){
    Node *current = head;
    for (int i = 0; i<position; i++)
    {
        current = current->next;
    }

    return current;
}
void appendNode(int n) {
    Node *newNode = new Node; //creating new node
    newNode->data = n;
    newNode->next = NULL;
    if (head == NULL)
    {
        head = newNode;
        return;
    }
    else {
        Node *current = head;
        while (current->next != NULL) {
            current = current->next;
        }
        current->next = newNode;

    }
    }

void insertNode(int n, int position) {
    Node *newNode = new Node;
    newNode->data = n;
    newNode->next = NULL;
    int size = sizeLinkedList();
    if (position = 0){
        if (head == NULL) {
            head = newNode;
        }
        else{
            newNode->next = head;
            head = newNode;
        }
    }

    else if (position == size) {
        appendNode(n);
    }

    else {
        Node *prevNode = getNode(position-1);
        Node *nextNode = getNode(position);
        prevNode->next = newNode;
        newNode->next = nextNode;

            }

        }


void deleteNode(int position) {
    Node *currentNode;

    int size = sizeLinkedList();
    if (size == 0) {
        return;
    }
    if (position == 0) {
        currentNode = head->next;
        head = currentNode;
    }
    else if (position == size-1) {
        getNode(position - 1)->next = NULL;
        delete getNode(position);

            }
    else {
        getNode(position - 1)->next = getNode(position+1);
        delete getNode(position);
    }
        }




//making a dynamic array only via pointers in VC++
    void makeArray() {
    int* m = NULL;
    int n;
    cout << "how many entries are there?"<<endl;
    cin >> n;
    m = new int[n];
    int temp;
    for (int x = 0; x < n; x++){
        cout << "enter item:"<< x+1<< endl;
        cin >> temp;
        *(m + x) = temp;
    } 
    for (int x = 0; x < n; x++){
        cout << x+1 + ":" << "There is item: "<<*(m+x) << endl;

    }
    delete[]m;
}
int main() {
    int x;
    //makeArray();
    appendNode(1);
    appendNode(2);
    appendNode(32);
    appendNode(55);
    appendNode(66);
    //insertNode(2, 0);
    printLinkedList();
    deleteNode(3);
    printLinkedList();
    sizeLinkedList();
    cin >> x;

}

我只是想用一些练习函数来编写一个链接列表我的删除功能，最后一个其他语句不起作用，逻辑上我无法弄清楚为什么，至于我的插入函数，没有一个语句工作，甚至在头部或位置0都没有。但是附加项目，返回大小，打印列表，删除第一个和最后一个元素都有效。

谢谢！

Answer 1

sizeLinkedList将无法正常工作
您使用size作为不同范围的不同变量（在主范围内，在deleteNode内）。这非常令人困惑，尽管并非严格错误。

deleteNode

，此序列无效：
```
else if (position == size-1) {
  getNode(position - 1)->next = NULL;
  delete getNode(position);
  }
```
将next之前的节点上的position指针设置为NULL将干扰下一行中getNode(position)的尝试，因为它会根据{{1}遍历列表}}。解决方法是扭转这两行。

同样，next中的最后一个序列因类似原因无效，因为您正在修改下一个指针：

deleteNode

这里的解决方案是这样的：

else {
  getNode(position - 1)->next = getNode(position+1);
  delete getNode(position);  // this list traversal will skip the node to delete!
  }

我还重新编写了else { currentNode = getNode(position); getNode(position - 1)->next = getNode(position+1); delete currentNode; }函数，其中包含@ 0x499602D2提供的注释。

以下是您的代码的修改版本，其中您当前的序列已修复为insertNode：

main

链接列表插入/删除

1 个答案: