leetcode 19. Remove Nth Node From End of List

题意

题解

代码

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeNthFromEnd(ListNode* head, int n) {
if (head == NULL)
return NULL;
int len = 0;
ListNode *iter = head;
while (iter != NULL)
iter = iter->next, len++;
int nth = len - n;
int index = 0;
ListNode *pre = NULL;
iter = head;
while (index < nth)
{
pre = iter;
iter = iter->next;//loop times：nth-1 = len-n
index++;

}
if (iter == head)
return head->next;
else
{
pre->next = iter->next;
return head;
}
}
};