找到单链表倒数第n个节点,保证链表中节点的最少数量为n。
样例
给出链表 3->2->1->5->null和n = 2,返回倒数第二个节点的值1.
/** * Definition of ListNode * class ListNode { * public: * int val; * ListNode *next; * ListNode(int val) { * this->val = val; * this->next = NULL; * } * } */ class Solution { public: /* * @param head: The first node of linked list. * @param n: An integer * @return: Nth to last node of a singly linked list. */ ListNode * nthToLast(ListNode * head, int n) { // write your code here ListNode* pre,*p; pre=head,p=head; while(n--) { if(p) { p=p->next; } else { return NULL; } } while(p) { p=p->next; pre=pre->next; } return pre; } };