Python 程序员面试金典 面试题 02.02. 返回倒数第 k 个节点

Posted 2021-09-05 Drink_Coffee_Cat

笨办法：先遍历链表得出链表长度然后就可以了

class Solution:
    def kthToLast(self, head: ListNode, k: int) -> int:
        cur = head
        cnt = 1

        while cur.next:
            cnt += 1
            cur = cur.next
        
        cur = head
        for i in range(cnt - k):
            cur = cur.next
        
        return cur.val

最佳解法：快慢指针

class Solution:
    def kthToLast(self, head: ListNode, k: int) -> int:
        fast = head
        slow = head
        while k > 0:
            fast = fast.next
            k -= 1
        while fast != None:
            fast = fast.next
            slow = slow.next
        return slow.val