Leetcode|剑指 Offer 22. 链表中倒数第k个节点

class Solution {
public:
    ListNode* getKthFromEnd(ListNode* head, int k) {
        int n = 0;
        auto node = head;
        while (node) {
            node = node->next;
            n++;
        }
        for (int i = 0; i < n; i++) {
            if (i == n - k) return head;
            head = head->next;
        }
        return nullptr;
    }
};

class Solution {
public:
    ListNode* getKthFromEnd(ListNode* head, int k) {
        auto preK = head;
        auto cur = head;
        for (int i = 0; i < k; i++)
            cur = cur->next;
        while (cur) {
            cur = cur->next;
            preK = preK->next;
        }
        return preK;
    }
};