剑指 Offer 22. 链表中倒数第k个节点

题意

返回链表的倒数第K个节点，索引从1开始

思路

• 采用链表中的快慢指针法，让快的指针先走k步
• 如下所示⬇️

1->2->3->4  , k = 2时
//1.快指针先走2步
        1->2->3->4
              ^
              |
             fast
//2.快慢指针一起出发直到fast指向NULL
        1->2->3->4
                      ^
                      |
                    fast
              ^
              |
            slow

代码

class Solution {
public:
    ListNode* getKthFromEnd(ListNode* head, int k) {
        ListNode* fast = head;
        ListNode* slow = head;
        while(k--) {
            fast = fast->next;
        }   //快指针先走k步
        while(fast) {
            fast = fast->next;
            slow = slow->next;
        }   //快慢指针一起出发
        return slow;
    }
};