从指定位置开始输出

输入1，则跳过第一个从第二个开始输出，输入-1，则把最后一个放在最前面，然后开始输出。。。

#define LIST "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

typedef struct DulNode
{
    char data;
    struct DulNode *prior;
    struct DulNode *next; 
 }DulNode;
 
void circle_init(DulNode *head);
void circle_print(DulNode *head, const int startNum);
void circle_des(DulNode *head);
 
int main()
{
    DulNode head = {'0', &head, &head};
    int start = 0;
    circle_init(&head);
    circle_print(&head, start);
    
    printf("输入跳过字符数量：");
    scanf("%d", &start);
    
    circle_print(&head, start);
    circle_des(&head);
    return 0;
}

void circle_init(DulNode *head)
{
    DulNode *p = head;
    int len = strlen(LIST);
    int i = 0;
    
    for(i=0; i<len; i++)
    {
        p->next = (DulNode *)malloc(sizeof(DulNode));
        p->next->next = head->prior;
        p->next->prior = p;
        head->prior = p->next;
        
        p = p->next;
        p->data = LIST[i];
    }
    
    p->next = head->next;
    head->next->prior = p;
}

void circle_print(DulNode *head, const int startNum)
{
    DulNode *p = head->next;
    DulNode *start = NULL;
    int i = startNum;
    
    if(i>0) {
        while(i)
        {
            p = p->next;
            i--;
        }
    }else {
        while(i)
        {
            p = p->prior;
            i++;
        }
    }
    
    start = p;
    do {
        printf("%c ", p->data);
        p = p->next;
    }while(p != start);
    printf("
");
}

void circle_des(DulNode *head)
{
    DulNode *p = head->next;
    DulNode *q = NULL;
    
    do {
        q = p->next;
        free(p);
        p = q;
    }while(p != head->next);
    head->next  = head;
    head->prior = head;
}

后来才知道，其实不用定义一个全局的字符串，可以直接用ASCII码赋值，即‘A’+1,即可得到'B'。。。。。。