RemoveDuplicatesFromSortedList.swift

/**
 * Question Link: https://leetcode.com/problems/remove-duplicates-from-sorted-list/
 * Primary idea: Iterate the list, jump over duplicates by replacing next with next.next
 * Time Complexity: O(n), Space Complexity: O(1)
 *
 * Definition for singly-linked list.
 * public class ListNode {
 *     public var val: Int
 *     public var next: ListNode?
 *     public init(_ val: Int) {
 *         self.val = val
 *         self.next = nil
 *     }
 * }
 */

class RemoveDuplicatesFromSortedList {
    func deleteDuplicates(_ head: ListNode?) -> ListNode? {
        guard let head = head else {
            return nil
        }
    
        var curt = head
        
        while curt.next != nil {
            if curt.next!.val == curt.val {
                curt.next = curt.next!.next
            } else {
                curt = curt.next!
            }
        }
        
        return head
    }
}