在C ++中反向双向链接列表 [英] Reverse doubly-link list in C++

问题描述

我一直在努力弄清楚如何颠倒双向链表的顺序，但由于某种原因，在我的函数 void reverse（）中运行while循环一次，然后由于某种原因崩溃。要回答一些问题，我是自我教导与我兄弟的帮助。这不是所有的代码，但我有一个 display（）函数按时间顺序从 start_ptr 和启动某些功能的开关。

I've been trying to figure out how to reverse the order of a doubly-linked list, but for some reason, in my function void reverse() runs while loop once and then crashes for some reason. To answer some questions ahead, I'm self-teaching myself with my brothers help. This isn't all of the code, but I have a display() function which prints all nodes chronologically from start_ptr and a switch which activates certain functions like

    case 1 : add_end(); break;
    case 2 : add_begin(); break;
    case 3 : add_index(); break;
    case 4 : del_end(); break;
    case 5 : del_begin(); break;
    case 6 : reverse(); break;

这是我的代码的geist：

This is the geist of my code:

#include <iostream>
using namespace std;

struct node
{
    char name[20];
    char profession[20];
    int age;
    node *nxt;
    node *prv;
};

node *start_ptr = NULL;

void pswap (node *pa, node *pb)
{
    node temp = *pa;
    *pa = *pb;
    *pb = temp;
    return;
}

void reverse()
{
    if(start_ptr==NULL)
    {
        cout << "Can't do anything" << endl;
    }
    else if(start_ptr->nxt==NULL)
    {
        return;
    }
    else
    {
        node *current = start_ptr;
        node *nextone = start_ptr;
        nextone=nextone->nxt->nxt;
        current=current->nxt;
        start_ptr->prv=start_ptr->nxt;
        start_ptr->nxt=NULL;
        //nextone=nextone->nxt;
        while(nextone->nxt!= NULL)
        {
            pswap(current->nxt, current->prv);
            current=nextone;
            nextone=nextone->nxt;
        }
        start_ptr=nextone;
    }
}

推荐答案

this：

node *ptr = start_ptr;
while (ptr != NULL) {
    node *tmp = ptr->nxt;
    ptr->nxt = ptr->prv;
    ptr->prv = tmp;
    if (tmp == NULL) {
        end_ptr = start_ptr;
        start_ptr = ptr;
    }
    ptr = tmp;
}

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