剑指Offer22:链表中倒数第k个节点(Golang/Python/C#)

原题连接：剑指Offer22:链表中倒数第k个节点

• 时间复杂度O(N):N为链表长度;总体看，former走了N步，latter 走了(N 一k)步。
• 空间复杂度O(1):双指针former , latter使用常数大小的额外空间。

Golang

package main

type ListNode struct {
	Val  int
	Next *ListNode
}
func getKthFromEnd(head *ListNode, k int) *ListNode {
	if head == nil {
		return head
	}
	former := head
	latter := head
	for i := 0; i < k; i++ {
		former = former.Next
	}
	for ; former != nil; {
		latter = latter.Next
		former = former.Next
	}
	return latter
}

Python

class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None


class Solution:
    def getKthFromEnd(self, head: ListNode, k: int) -> ListNode:
        if not head: return head
        former, latter = head, head
        for i in range(k):
            former = former.next
        while former:
            latter, former = latter.next, former.next
        return latter

C#

public class ListNode
{
    public int val;
    public ListNode next;
    public ListNode(int x) { val = x; }
}

public class Solution
{
    public ListNode GetKthFromEnd(ListNode head, int k)
    {
        if (head == null) return null;
        var former = head;
        var latter = head;
        for (int i = 0; i < k; i++) {
            former = former.next;
        }
        while (former != null) {
            latter = latter.next;
            former = former.next;
        }
        return latter;
    }
}