83. Remove Duplicates from Sorted List

Given a sorted linked list, delete all duplicates such that each element appear only once.

Example 1:

Input: 1->1->2
Output: 1->2

Example 2:

Input: 1->1->2->3->3
Output: 1->2->3

# Definition for singly-linked list.
# class ListNode
#     attr_accessor :val, :next
#     def initialize(val = 0, _next = nil)
#         @val = val
#         @next = _next
#     end
# end
# @param {ListNode} head
# @return {ListNode}
def delete_duplicates(head)
  prev = nil
  cur = head
  while(cur)
    if prev && prev.val == cur.val
      prev.next = cur.next
    else
      prev = cur
    end
    cur = cur.next
  end
  head
end