删除单链表中偶数节点

题目意思就是：

删除链表中第2个节点，第4个节点......，即删除所有第偶数个节点

#include <stdio.h>
#include <stdlib.h>

#define LEN 8
typedef struct node node_t;

struct node{  
    int val;  
    node_t *next;  
};  

//delete even node
void delete_even_node(node_t* head);

int main()
{
    node_t** arr = (node_t**)malloc(sizeof(node_t*)*LEN);
    arr[0] = (node_t*)malloc(sizeof(node_t));
    arr[0]->val = 0;
    int i;
    for(i = 1; i < LEN; i++)
    {
        arr[i] = (node_t*)malloc(sizeof(node_t));
        arr[i]->val = i;
        arr[i - 1]->next = arr[i];
    }
    arr[LEN - 1]->next = NULL;
    arr[LEN - 1]->val = 7;

    delete_even_node(arr[0]);

    while(arr[0] != NULL)
    {
        printf("%d\n", arr[0]->val);
        arr[0] = arr[0]->next;
    }

    return 0;
}

void delete_even_node(node_t* head)
{
    if(head != NULL)
    {
        //q is after p
        node_t* p = head;
        node_t* q = head->next;

        while(q != NULL)
        {
            p->next = q->next;
            p = q->next;

            free(q);

            if(p != NULL)
                q = p->next;
            else
                q = NULL;
        }
    }
}