https://leetcode.com/problems/remove-nth-node-from-end-of-list/

1. Use one-pass:

  1. //4 ms    10.4 MB
  3. /**
  4.  * Definition for singly-linked list.
  5.  * struct ListNode {
  6.  *     int val;
  7.  *     ListNode *next;
  8.  *     ListNode() : val(0), next(nullptr) {}
  9.  *     ListNode(int x) : val(x), next(nullptr) {}
  10.  *     ListNode(int x, ListNode *next) : val(x), next(next) {}
  11.  * };
  12.  */
  13. class Solution {
  14. public:
  15.     ListNode* removeNthFromEnd(ListNode* head, int n) {  
  16.         if(!head || (!head->next && n == 1)) return NULL;
  18.         ListNode* dummy = new ListNode(-1);
  19.         dummy->next = head;
  21.         ListNode* curr1 = head;
  22.         ListNode* curr2 = head;
  23.         ListNode* prev = dummy;
  25.         for(int i = 1; i < n; i++)
  26.             curr1 = curr1->next;
  28.         while(curr1->next){
  29.             prev = curr2;
  30.             curr1 = curr1->next;
  31.             curr2 = curr2->next;
  32.         }
  34.         prev->next = curr2->next;
  36.         return dummy->next;
  37.     }
  38. };