思路:先加个哨兵结点(好处是可以避免很多特殊情况的特判),快慢指针,快指针先走n步,然后快慢一起走,直到快指针走到最后。
时间复杂度:O(n)
//先加个哨兵结点,快慢指针,快指针先走n步,然后快慢一起走,直到快指针走到最后
//时间复杂度O(n)
class Solution {
public:
ListNode* removeNthFromEnd(ListNode* head, int n) {
ListNode*first = new ListNode(0);
first->next = head;
ListNode*fast = first, *slow = first;
//先让fast走n步
while (n--)
{
fast = fast->next;
}
//然后一起走
while (fast->next != NULL)
{
fast = fast->next;
slow = slow->next;
}
ListNode*temp = slow->next;
slow->next = slow->next->next;
delete temp;
temp = NULL;
return first->next;
}
};