[Lc]面试题22链表中倒数第k个节点

题目

题解

快慢指针

• 时间复杂度$O(n)$
• 空间复杂度$O(1)$

class Solution {
public:
    ListNode* getKthFromEnd(ListNode* head, int k) {
        if(k==0 || !head) return nullptr;
        ListNode *fast = head, *slow = head;
        int n = 0;
        while(fast){
            if(n >= k) slow = slow->next;
            fast = fast->next;
            n++;
        }
        if(n<k) return nullptr;
        return slow;


    }
};