题解 | #链表中倒数最后k个结点#

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param pHead ListNode类
     * @param k int整型
     * @return ListNode类
     */
    ListNode* FindKthToTail(ListNode* pHead, int k) {
        // write code here
        ListNode* left = pHead;
        ListNode* right = pHead;
        if (pHead==NULL||k==0) {
            return nullptr;
        }
        for (int i=1; i <=k; i++) {
            if (right->next!=NULL) {
            right = right->next;
            }
            else{ if(i<k)
                {return pHead=nullptr;}
                else {
                return pHead;
                }
            }  
        }
        while (right->next != NULL) {
            right = right->next;
            left = left->next;
        }
        return left->next;
    }
};