Description
https://oj.leetcode.com/problems/remove-nth-node-from-end-of-list/
Difficulty: 2.5/5.0
Analysis and solution
The problem requires to remove the node from the end of the list within one sweep. So we set two pointers with one being nodes ahead the other.
/**
* 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)
return head;
ListNode *pt1 = head, *pt2 = head, *newHead = new ListNode(0);
newHead->next = head;
ListNode *pt3 = newHead;
while(n--)
pt2 = pt2->next;
while(pt2){
pt1 = pt1->next;
pt3 = pt3->next;
pt2 = pt2->next;
}
pt3->next = pt1->next;
delete pt1;
head = newHead->next;
delete newHead;
return head;
}
};