day4 移出倒数第n个节点

ListNode* removeNthFromEnd(ListNode* head, int n) {

ListNode* dummyHead = new ListNode(0);

dummyHead->next = head;

ListNode* slow = dummyHead;

ListNode* fast = dummyHead;

while(n-- && fast != NULL) {

fast = fast->next;

}

fast = fast->next; // fast再提前走一步，因为需要让slow指向删除节点的上一个节点

while (fast != NULL) {

fast = fast->next;

slow = slow->next;

}

slow->next = slow->next->next;

// ListNode *tmp = slow->next; C++释放内存的逻辑

// slow->next = tmp->next;

// delete tmp;

return dummyHead->next;

}