203. Remove Linked List Elements(E)

important: 8

tags: Linked List

tags: Amazon FB Apple Google Bloomberg Microsoft

Leetcode 203

Q: Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

Hint: Use "Dummy Node" to be the another linked list head.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */

1. Sentinel Node

class Solution {
    public ListNode removeElements(ListNode head, int val) {
        //Use dummy node to delete the val nodes
        
        ListNode dummy=new ListNode(0);
        dummy.next=head;
        ListNode prev=dummy;
        ListNode cur=head;
        
        while(cur!=null){
            if(cur.val==val){
                prev.next=cur.next;
                cur=cur.next;
            }
            else{
                prev=cur;
                cur=cur.next;
            }
        }       
        return dummy.next;
    }
}

Time complexity :O(N) Space complexity :O(1)