输入一个链表，反转链表后，输出新链表的表头

/* reverse_link_list.c
 *
 * Copyright (c) 2020
 * Author: plant
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
 
#include <stdio.h>
#include <stdlib.h>

typedef int ELEM_TYPE;

typedef struct _lnode
{
    ELEM_TYPE data;
    struct _lnode* next;
} lnode, * link_list;

link_list reverse_link_list(link_list head_in)
{
    link_list head_out = NULL;

    if (head_in == NULL) return NULL;

    lnode* curr_node = head_in;
    lnode* prev_node = NULL;
    lnode* next_node = NULL;
    while (curr_node != NULL)
    {
        next_node = curr_node->next;
        if (curr_node->next == NULL)// if the list only have a head node
        {
            head_out = curr_node;
        }
        curr_node->next = prev_node;
        prev_node = curr_node;
        curr_node = next_node;

    }

    return head_out;
}

int main()
{
    link_list list1;

    lnode* nodes[7];
    lnode* temp_node;
    for (int i = 0; i < 7; i++)
    {
        nodes[i] = (lnode*)malloc(sizeof(lnode));
        nodes[i]->data = i;
    }
    // 1->2->3->4->5->6->7
    for (int i = 0; i < 6; i++)
    {
        nodes[i]->next = nodes[i + 1];
    }
    nodes[6]->next = NULL;
    list1 = nodes[0];

    temp_node = reverse_link_list(list1);

    while (temp_node != NULL)
    {
        printf("node:\t%d\n", temp_node->data);
        temp_node = temp_node->next;
    }

    return 0;
}