https://leetcode.com/problems/remove-linked-list-elements/

1. Use two pointers:

  1. //36 ms    10.6 MB
  3. /**
  4.  * Definition for singly-linked list.
  5.  * struct ListNode {
  6.  *     int val;
  7.  *     ListNode *next;
  8.  *     ListNode(int x) : val(x), next(NULL) {}
  9.  * };
  10.  */
  11. class Solution {
  12. public:
  13.     ListNode* removeElements(ListNode* head, int val) {
  14.         if(!head) return NULL;
  16.         ListNode* dummy = new ListNode(-1);
  17.         dummy->next = head;
  19.         ListNode* curr = dummy->next;
  20.         ListNode* prev = dummy;
  22.         while(curr){
  23.             if(curr && curr->val == val){
  24.                 prev->next = curr->next;
  25.                 curr->next = NULL;
  26.                 curr = prev->next;
  27.             } else{
  28.                 curr = curr->next;
  29.                 prev = prev->next;
  30.             }
  31.         }
  33.         return dummy->next;
  34.     }
  35. };