Leetcode 203 Remove Linked List Elements

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

通过判断p.next的值是否相等于提供的值确定p的下一个node可以省一个指针。

var removeElements = function(head, val) {
    if(!head)
        return null
    var dummy = new ListNode()
    dummy.next = head
    var p = dummy
    while(p.next)
        if(p.next.val===val)
            p.next = p.next.next
        else
            p = p.next
    return dummy.next
};

也可以使用双指针previous,current。每次判断current是否相等于提供的值然后确定previous的下一个node。

def remove_elements(head, val)
    return if not head
    dummy = ListNode.new(0)
    dummy.next = head
    previous = dummy
    current = head
    while current
        if current.val == val
            previous.next = current.next
        else
            previous = current
        end
        current = current.next
    end
    dummy.next
end