C 无头链表，右移位数。得到新串。

改变字符的顺序，不用额外存储空间。
改变前：a1 a2......am b1 b2......bn
改变后：b1 b2......bn a1 a2......am
如A B C D E F G变成E F G A B C D。用链表实现。

#define _CRT_SECURE_NO_WARNINGS
#include 
#include
typedef struct Node {
    char val;
    struct Node* next;  
}ListNode;

ListNode* rotate(ListNode* head, int k) {
    if (k == 0 || head == NULL || head->next == NULL) return head;
    int n = 1;
    ListNode* iter = head;
    while (iter->next != NULL) {
        iter = iter->next;
        n++;
    }
    int add = n - k % n;
    if (add == n) return head;
    iter->next = head;
    while (add--) iter = iter->next;
    ListNode* ret = iter->next;
    iter->next = NULL;
    return ret;
}

ListNode* creatlist_r(char str[],int n)
{
    int i;
    ListNode*head=NULL,*p,*r=NULL;    
    for (i = 0; i < n; i++)
    {
        p= (ListNode*)malloc(sizeof(ListNode));
        p->val = str[i];
        p->next = NULL;
        if (head == NULL)
        {
            head = p; 
            r = p;
        }
        r->next = p;
        r = p;
    }
    return head;
}
void print(ListNode* head)
{
    if (head == NULL)
        return;
    ListNode* p = head;
    while (p)
    {
        printf("%c ",p->val);
        p = p->next;
    }
    printf("n");
}
int main()
{  
    ListNode* head;
    char str[] = { 'A','B','C','D','E','F','G' };
    head=creatlist_r(str,7);
    head = rotate(head,3);//右移3  
    print(head);
    return 0;
}