程序代码：

# include <stdio.h>
# include <stdlib.h>
# define LEN sizeof(struct ring)
struct ring
{
    int num;
    struct ring *next;
};
void blist(struct ring *head, int n)        //建立环状链表
{
    int i;
    struct ring *pre = head, *new, *fin;  
    for(i = 0; i < n; i++)                
    {
        pre->num = i+1;
        fin = pre;
        new = malloc(LEN);
        pre->next = new;
        pre = new;
    }
    fin->next = head;
}
void del(struct ring *head)        //每第三个节点删除 
{
    struct ring *pre, *bef, *t;
    pre = bef = head;
    while(pre->next != pre)
    {
        pre = bef = pre->next;
        pre = pre->next;
        t = pre;
        free(pre);
        pre = bef->next = t->next;
        
            
    }
    printf("剩下最后一人的原序号为：NO.%d\n", pre->num);
}
int main()
{
    struct ring *head;
    int n;
    printf("请输入参与的人数：");
    scanf("%d", &n);
    head = malloc(LEN);
    blist(head, n);
    del(head);
    //print(head);
    return 0;
}