203 LeetCode Java: Remove Linked List Elements – Easy

Problem:

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

Thoughts;

This is a very simple linked list problem. Using a fakeHead is helping a lot for edge cases.

For many linked list problem, it’s always good practice to add a fakeHead in front in avoid null pointer problem in edge cases.

Solutions:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 /**

• Definition for singly-linked list.

• public class ListNode {

• int val;

• ListNode next;

• ListNode(int x) { val = x; }

• } */ public class Solution { public ListNode removeElements(ListNode head, int val) { ListNode fakeHead = new ListNode(-1); fakeHead.next = head;

    ListNode parent = fakeHead;
    ListNode node = head;
    while (node != null){
        if (node.val == val)
            parent.next = node.next;
        else
            parent = node;
    node = node.next;
    }//while
    return fakeHead.next;

  } }

Updated: 12/31/2016
Improve logic.

```java
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode removeElements(ListNode head, int val) {
        ListNode fakeHead = new ListNode(-1);
        fakeHead.next = head;
        ListNode node = fakeHead;
        while (node.next != null) {
            if (node.next.val == val) {
                node.next = node.next.next;
            } 
            else {
                node = node.next;
            }
        }
        return fakeHead.next;
    }
}
```