5、单链表的反转

代码：

#include "stdafx.h"
#include<windows.h>
#include<iostream>
#include<vector>

using namespace std;

struct list_node
{
    int value;
    list_node *next;
};

list_node *init_list(int len)
{
    list_node *head, *p, *q;

    p = (list_node *)malloc(sizeof(list_node));
    p->value = 0;
    head = p;

    for (int i = 1; i < len; i++)
    {
        q = (list_node *)malloc(sizeof(list_node));
        q->value = 2 * i;
        p->next = q;
        p = q;
    }
    p->next = NULL;

    return head;
}

int show_list(list_node *head)
{
    if (head == NULL) return 0;

    list_node *p = head;

    while (p)
    {
        printf("%4d", p->value);
        p = p->next;
    }
    printf("\n");

    return 0;
}

list_node *reverse_list(list_node *head)
{
    struct list_node *prev = NULL;
    struct list_node *current = head;

    while (current)
    {
        struct list_node *node = current->next;
        current->next = prev;
        prev = current;
        current = node;
    }

    return prev;
}

int main()
{
    list_node *head = init_list(10);
    show_list(head);
    head = reverse_list(head);
    show_list(head);

    system("pause");
    return 0;
}