[Swift] Remove Nth Node From End of List

Given the head of a linked list, remove the n$^t$$^h$ node from the end of the list and return its head.

Example 1:

Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]

Example 2:

Input: head = [1], n = 1
Output: []

Example 3:

Input: head = [1,2], n = 1
Output: [1]

Constraints:

• The number of nodes in the list is sz.
• 1 <= sz <= 30
• 0 <= Node.val <= 100
• 1 <= n <= sz

풀러가기

문제 이해

LinkedList 의 마지막에서 n 번째 해당하는 노드를 제거

코드

func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
  var head: ListNode? = head
  
  var node: ListNode? = head
  var count = 0
  while let current = node {
    node = current.next
    count += 1
  }
  
  count -= n
  if count <= 0 {
    return head?.next
  }
  
  var i = 0
  node = head
  while let current = node, i != count - 1 {
    node = current.next
    i += 1
  }
  
  node?.next = node?.next?.next
  
  return head
}

풀이

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