反转链表

      又见翻转链表，这回是给定接口的递归和非递归翻。比之前那篇反转链表多了接口限制。

#include <iostream>

using namespace std;

typedef struct node LinkNode;
struct node
{
    int data;
    LinkNode *next;
};

LinkNode *reverse_link(LinkNode *head)
{
    if (head == NULL) return NULL;

    LinkNode *prev = NULL, *next = head->next;

    while (next != NULL)
    {
        head->next = prev;
        prev = head;
        head = next;
        next = head->next;
    }

    head->next = prev;

    return head;
}

LinkNode *reverse_link_recursive(LinkNode *head)
{
    if (head == NULL) return NULL;
    if (head->next == NULL) return head;

    LinkNode *next = head->next;
    LinkNode *reverse_head = reverse_link_recursive(next);
    next->next = head;
    head->next = NULL;

    return reverse_head;
}

void print_link(const LinkNode *head)
{
    while (head != NULL)
    {
        cout << head->data << " ";
        head = head->next;
    }

    cout << endl;
}

int main()
{
    LinkNode o[6];

    for (int i = 0; i < 5; ++i)
    {
        o[i].data = i;
        o[i].next = &o[i + 1];
    }
    o[4].next = NULL;

    print_link(&o[0]);
    LinkNode *head = reverse_link(&o[0]);
    print_link(head);
    head = reverse_link_recursive(head);
    print_link(head);

    return 0;
}