力扣00019.删除链表的倒数第 N 个结点

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删除链表的倒数第 N 个结点、链表、双指针、中等

题目描述

给你一个链表，删除链表的倒数第 n 个结点，并且返回链表的头结点。

示例 1：

输入：head = [1,2,3,4,5], n = 2
输出：[1,2,3,5]

示例 2：

输入：head = [1], n = 1
输出：[]

示例 3：

输入：head = [1,2], n = 1
输出：[1]

提示：

  • 链表中结点的数目为 sz
  • 1 <= sz <= 30
  • 0 <= Node.val <= 100
  • 1 <= n <= sz

进阶：你能尝试使用一趟扫描实现吗？

解决方法

C++

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* fast = dummy;
        ListNode* slow = dummy;
        for (int i = 0; i <= n; ++i) {
            fast = fast->next;
        }
        while (fast != nullptr) {
            slow = slow->next;
            fast = fast->next;
        }
        ListNode* toDelete = slow->next;
        slow->next = slow->next->next;
        delete toDelete;
        return dummy->next;
    }
};

结果

执行用时 : 0 ms, 击败 100.00% 使用 C++ 的用户

内存消耗 : 10.97 MB, 击败 11.94% 使用 C++ 的用户

Java

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode fast = dummy;
        ListNode slow = dummy;
        for (int i = 0; i <= n; i++) {
            fast = fast.next;
        }
        while (fast != null) {
            slow = slow.next;
            fast = fast.next;
        }
        slow.next = slow.next.next;
        return dummy.next;
    }
}

结果

执行用时 : 0 ms, 击败 100.00% 使用 Java 的用户

内存消耗 : 40.65 MB, 击败 7.23% 使用 Java 的用户

Python

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# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def removeNthFromEnd(self, head, n):
        dummy = ListNode(0)
        dummy.next = head
        fast = slow = dummy
        for i in range(n + 1):
            fast = fast.next
        while fast != None:
            slow = slow.next
            fast = fast.next
        slow.next = slow.next.next
        return dummy.next

结果

执行用时 : 24 ms, 击败 29.15% 使用 Python 的用户

内存消耗 : 13.18 MB, 击败 7.92% 使用 Python 的用户

Python3

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# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def removeNthFromEnd(self, head: Optional[ListNode], n: int) -> Optional[ListNode]:
        dummy = ListNode(0)
        dummy.next = head
        fast = slow = dummy
        for i in range(n + 1):
            fast = fast.next
        while fast:
            slow = slow.next
            fast = fast.next
        slow.next = slow.next.next
        return dummy.next

结果

执行用时 : 40 ms, 击败 81.53% 使用 Python3 的用户

内存消耗 : 16.98 MB, 击败 8.12% 使用 Python3 的用户

C

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* removeNthFromEnd(struct ListNode* head, int n) {
    struct ListNode* dummy = (struct ListNode*)malloc(sizeof(struct ListNode));
    dummy->next = head;
    struct ListNode* fast = dummy;
    struct ListNode* slow = dummy;
    for (int i = 0; i <= n; ++i) {
        fast = fast->next;
    }
    while (fast != NULL) {
        slow = slow->next;
        fast = fast->next;
    }
    struct ListNode* toDelete = slow->next;
    slow->next = slow->next->next;
    free(toDelete);
    return dummy->next;
}

结果

执行用时 : 0 ms, 击败 100.00% 使用 C 的用户

内存消耗 : 6.30 MB, 击败 82.47% 使用 C 的用户

C#

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    public ListNode RemoveNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode fast = dummy;
        ListNode slow = dummy;
        for (int i = 0; i <= n; i++) {
            fast = fast.next;
        }
        while (fast != null) {
            slow = slow.next;
            fast = fast.next;
        }
        slow.next = slow.next.next;
        return dummy.next;
    }
}

结果

执行用时 : 68 ms, 击败 85.59% 使用 C# 的用户

内存消耗 : 40.11 MB, 击败 10.36% 使用 C# 的用户

JavaScript

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/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function(head, n) {
    let dummy = new ListNode(0);
    dummy.next = head;
    let fast = dummy;
    let slow = dummy;
    for (let i = 0; i <= n; i++) {
        fast = fast.next;
    }
    while (fast !== null) {
        slow = slow.next;
        fast = fast.next;
    }
    slow.next = slow.next.next;
    return dummy.next;
};

结果

执行用时 : 68 ms, 击败 40.96% 使用 JavaScript 的用户

内存消耗 : 49.12 MB, 击败 7.04% 使用 JavaScript 的用户

TypeScript

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/**
 * Definition for singly-linked list.
 * class ListNode {
 *     val: number
 *     next: ListNode | null
 *     constructor(val?: number, next?: ListNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.next = (next===undefined ? null : next)
 *     }
 * }
 */

function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
    const dummy = new ListNode(0);
    dummy.next = head;
    let fast: ListNode | null = dummy;
    let slow: ListNode | null = dummy;
    for (let i = 0; i <= n; i++) {
        if (fast !== null) {
            fast = fast.next;
        }
    }
    while (fast !== null) {
        slow = slow.next;
        fast = fast.next;
    }
    if (slow !== null && slow.next !== null) {
        slow.next = slow.next.next;
    }
    return dummy.next;
}

结果

执行用时 : 72 ms, 击败 43.59% 使用 TypeScript 的用户

内存消耗 : 50.61 MB, 击败 8.16% 使用 TypeScript 的用户

PHP

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/**
 * Definition for a singly-linked list.
 * class ListNode {
 *     public $val = 0;
 *     public $next = null;
 *     function __construct($val = 0, $next = null) {
 *         $this->val = $val;
 *         $this->next = $next;
 *     }
 * }
 */
class Solution {

    /**
     * @param ListNode $head
     * @param Integer $n
     * @return ListNode
     */
    function removeNthFromEnd($head, $n) {
        $dummy = new ListNode(0);
        $dummy->next = $head;
        $fast = $dummy;
        $slow = $dummy;
        for ($i = 0; $i <= $n; $i++) {
            $fast = $fast->next;
        }
        while ($fast != null) {
            $slow = $slow->next;
            $fast = $fast->next;
        }
        $slow->next = $slow->next->next;
        return $dummy->next;
    }
}

结果

执行用时 : 8 ms, 击败 58.70% 使用 PHP 的用户

内存消耗 : 19.46 MB, 击败 6.52% 使用 PHP 的用户

Swift

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public var val: Int
 *     public var next: ListNode?
 *     public init() { self.val = 0; self.next = nil; }
 *     public init(_ val: Int) { self.val = val; self.next = nil; }
 *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
 * }
 */
class Solution {
    func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
        let dummy = ListNode(0)
        dummy.next = head
        var fast: ListNode? = dummy
        var slow: ListNode? = dummy
        for _ in 0...n {
            fast = fast?.next
        }
        while fast != nil {
            slow = slow?.next
            fast = fast?.next
        }
        slow?.next = slow?.next?.next
        return dummy.next
    }
}

结果

执行用时 : 4 ms, 击败 97.71% 使用 Swift 的用户

内存消耗 : 15.30 MB, 击败 6.29% 使用 Swift 的用户

Kotlin

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/**
 * Example:
 * var li = ListNode(5)
 * var v = li.`val`
 * Definition for singly-linked list.
 * class ListNode(var `val`: Int) {
 *     var next: ListNode? = null
 * }
 */
class Solution {
    fun removeNthFromEnd(head: ListNode?, n: Int): ListNode? {
        val dummy = ListNode(0)
        dummy.next = head
        var fast: ListNode? = dummy
        var slow: ListNode? = dummy
        for (i in 0..n) {
            fast = fast?.next
        }
        while (fast != null) {
            slow = slow?.next
            fast = fast?.next
        }
        slow?.next = slow?.next?.next
        return dummy.next
    }
}

结果

执行用时 : 156 ms, 击败 88.00% 使用 Kotlin 的用户

内存消耗 : 33.89 MB, 击败 51.00% 使用 Kotlin 的用户

Dart

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/**
 * Definition for singly-linked list.
 * class ListNode {
 *   int val;
 *   ListNode? next;
 *   ListNode([this.val = 0, this.next]);
 * }
 */
class Solution {
  ListNode? removeNthFromEnd(ListNode? head, int n) {
    ListNode? dummy = ListNode(0);
    dummy.next = head;
    ListNode? fast = dummy;
    ListNode? slow = dummy;
    for (int i = 0; i <= n; i++) {
      fast = fast!.next;
    }
    while (fast != null) {
      slow = slow!.next;
      fast = fast.next;
    }
    slow!.next = slow.next!.next;
    return dummy.next;
  }
}

结果

执行用时 : 388 ms, 击败 0.00% 使用 Dart 的用户

内存消耗 : 148.34 MB, 击败 85.71% 使用 Dart 的用户

Go

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/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func removeNthFromEnd(head *ListNode, n int) *ListNode {
	dummy := &ListNode{Val: 0, Next: head}
	fast, slow := dummy, dummy
	for i := 0; i <= n; i++ {
		fast = fast.Next
	}
	for fast != nil {
		fast = fast.Next
		slow = slow.Next
	}
	slow.Next = slow.Next.Next
	return dummy.Next
}

结果

执行用时 : 0 ms, 击败 100.00% 使用 Go 的用户

内存消耗 : 2.07 MB, 击败 83.45% 使用 Go 的用户

Ruby

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# 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
# @param {Integer} n
# @return {ListNode}
def remove_nth_from_end(head, n)
  dummy = ListNode.new(0)
  dummy.next = head
  fast = dummy
  slow = dummy
  (n + 1).times { fast = fast.next }
  while fast != nil
    slow = slow.next
    fast = fast.next
  end
  slow.next = slow.next.next
  return dummy.next
end

结果

执行用时 : 56 ms, 击败 100.00% 使用 Ruby 的用户

内存消耗 : 206.75 MB, 击败 16.67% 使用 Ruby 的用户

Scala

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/**
 * Definition for singly-linked list.
 * class ListNode(_x: Int = 0, _next: ListNode = null) {
 *   var next: ListNode = _next
 *   var x: Int = _x
 * }
 */
object Solution {
  def removeNthFromEnd(head: ListNode, n: Int): ListNode = {
    val dummy = new ListNode()
    dummy.next = head
    var fast = dummy
    var slow = dummy
    for (i <- 0 to n) {
      fast = fast.next
    }
    while (fast != null) {
      slow = slow.next
      fast = fast.next
    }
    slow.next = slow.next.next
    dummy.next
  }
}

结果

执行用时 : 556 ms, 击败 12.50% 使用 Scala 的用户

内存消耗 : 56.24 MB, 击败 62.50% 使用 Scala 的用户

Rust

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// Definition for singly-linked list.
// #[derive(PartialEq, Eq, Clone, Debug)]
// pub struct ListNode {
//   pub val: i32,
//   pub next: Option<Box<ListNode>>
// }
//
// impl ListNode {
//   #[inline]
//   fn new(val: i32) -> Self {
//     ListNode {
//       next: None,
//       val
//     }
//   }
// }
impl Solution {
    pub fn remove_nth_from_end(head: Option<Box<ListNode>>, n: i32) -> Option<Box<ListNode>> {
        let mut dummy = Box::new(ListNode { val: 0, next: head });
        unsafe {
            let mut slow = &mut dummy as *mut Box<ListNode>;
            let mut fast = &mut dummy as *mut Box<ListNode>;
            for _ in 0..n {
                fast = (*fast).next.as_mut().unwrap();
            }
            while (*fast).next.is_some() {
                fast = (*fast).next.as_mut().unwrap();
                slow = (*slow).next.as_mut().unwrap();
            }
            (*slow).next = (*slow).next.take().unwrap().next;
        }
        dummy.next
    }
}

结果

执行用时 : 0 ms, 击败 100.00% 使用 Rust 的用户

内存消耗 : 2.14 MB, 击败 16.30% 使用 Rust 的用户

Racket

暂时未解决

1

结果

执行用时 : ms, 击败 % 使用 Racket 的用户

内存消耗 : MB, 击败 % 使用 Racket 的用户

Erlang

暂时未解决

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结果

执行用时 : ms, 击败 % 使用 Erlang 的用户

内存消耗 : MB, 击败 % 使用 Erlang 的用户

Elixir

暂时未解决

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结果

执行用时 : ms, 击败 % 使用 Elixir 的用户

内存消耗 : MB, 击败 % 使用 Elixir 的用户