[Linked List]Remove Linked List Elements

Total Accepted: 43183 Total Submissions: 160460 Difficulty: Easy

Remove all elements from a linked list of integers that have value val.

Example
Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
Return: 1 --> 2 --> 3 --> 4 --> 5

(E) Remove Element (E) Delete Node in a Linked List

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        ListNode* p = head,*next=NULL,*pre=NULL;
        while(p && p->val==val){
            next = p->next;
            delete(p);
            p = next;
            head = p;
        }
        while(p){
            if(p->val == val){
                pre->next = p->next;
                delete(p);
                p = pre->next;
            }else{
                pre=p;
                p=p->next;
            }
        }
        return head;
    }
};

Next challenges: (M) Convert Sorted List to Binary Search Tree (H) Copy List with Random Pointer (E) Intersection of Two Linked Lists