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;
}

} ``````java 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; } }