[1669] Merge In Between Linked Lists

好像也不是什麼有意思的題目（thinking 圖）

前人可能測資比較親民所以速度都很快

貼過來用也跟我的一樣慢XD 沒有成就感，無趣XP

/**

* Definition for singly-linked list.

* struct ListNode {

* int val;

* struct ListNode *next;

* };

*/

struct ListNode* mergeInBetween(struct ListNode* list1, int a, int b, struct ListNode* list2){

int count = 0;

struct ListNode *ptr, *pre;

ptr = list1;

while (count < a)

{

pre = ptr;

ptr = ptr->next;

count ++;

}

pre->next = list2;

while (count <b)

{

ptr = ptr->next;

count++;

}

struct ListNode *l2tail=list2 ;

while (l2tail->next != NULL)

l2tail = l2tail->next;

l2tail ->next = ptr->next;

return list1;

}