[61] Rotate List

ㄟ～～～嗯～～～該說什麼好呢XD

奇怪我好像總是有多餘的檢查在回圈裡面？！

但是因為很快就accept了所以不想再追究了（遮臉）

C 真是 Linked list 的好朋友啊～～～～～

/**

* Definition for singly-linked list.

* struct ListNode {

* int val;

* struct ListNode *next;

* };

*/

struct ListNode* rotateRight(struct ListNode* head, int k){

if (head == NULL || k==0 || head->next == NULL)

return head;

int length=0;

struct ListNode* pRun = head;

while(pRun!=NULL)

{

length++;

if (pRun->next==NULL)

break;

pRun=pRun->next;

}

pRun->next=head;

int stop = length - k%length;

for(int rotate=0; rotate <stop;rotate++)

{

if (rotate+1 ==stop)

pRun = head;

head = head->next;

}

pRun->next = NULL;

return head;

}

[20240811 update] 重新寫了一次，整個思維好像很不一樣了呢（？）

struct ListNode* rotateRight(struct ListNode* head, int k){

int count =0;

struct ListNode* ptr = head;

struct ListNode* pre, *tail;

while (ptr != NULL)

{

pre = ptr;

ptr = ptr->next;

count++;

}

if (count <=1)

return head;

tail = pre;

int _k = k%count;

int step = 0;

ptr = head;

while (step < (count - _k))

{

pre = ptr;

ptr = ptr->next;

step++;

}

tail->next = head;

head = pre->next;

pre->next = NULL;

return head;

}

修改了一下扣的長度可以變短，但是count 要小心

/**

* Definition for singly-linked list.

* struct ListNode {

* int val;

* struct ListNode *next;

* };

*/

struct ListNode* rotateRight(struct ListNode* head, int k){

if (head == NULL || head ->next == NULL)

return head;

int count =0;

struct ListNode* ptr = head;

struct ListNode* pre;

while (ptr->next != NULL)

{

ptr = ptr->next;

count++;

}

count++;

ptr->next = head;

int _k = k%count;

int step = 0;

ptr = head;

while (step < (count - _k))

{

pre = ptr;

ptr = ptr->next;

step++;

}

head = pre->next;

pre->next = NULL;

return head;

}