问题描述:
Given a linked list, remove the nth node from the end of list and return its head.
For example,
Given linked list: 1->2->3->4->5, and n = 2.
After removing the second node from the end, the linked list becomes 1->2->3->5.
Note:
Given n will always be valid.
Try to do this in one pass.
思路:
题目看来挺简单,主要就是设置一个前行节点一个后行节点,同步控制两节点距离一直到链表末端。但是实践完成代码的思路上还是有一点点技巧和注意的。
这里我用了一个链表附加头节点,这样在删除头结点问题上可以很方便解决;然后注意要得到的节点应该是所要求删除节点的前一个节点;还有就是最后返回链表时,要返回更新后的head节点,因为head可能有改变。
代码:
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeNthFromEnd(ListNode* head, int n) {
ListNode* prehead = new ListNode(-1);
prehead->next = head;
ListNode* bias = prehead;
ListNode* targetpre = prehead;
//bias move forward n steps
for(int i = 0; i < n; i++)
{
if(bias == NULL) return head;
bias = bias->next;
}
//bias point to the end, at the same time, target point to the previous node of the nth from the end.
while(bias->next != NULL)
{
bias = bias->next;
targetpre = targetpre->next;
}
ListNode* temp = targetpre->next;
targetpre->next = temp->next;
head = prehead->next; //update the new head
delete temp;
delete prehead;
return head;
}
};