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Leetcode: Remove Nth Node From End of List

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.

分析:two pointers.

class Solution {public:    ListNode *removeNthFromEnd(ListNode *head, int n) {        if(head == NULL) return head;                ListNode *dummy = new ListNode(-1);        dummy->next = head;        
     //move fast pointer to (n+1)th node from the head ListNode
*fast = head; for(int i = 0; i < n; i++) fast = fast->next; //move fast to the end of the list ListNode *prev = dummy, *p = head; while(fast){ fast = fast->next; prev = p; p = p->next; } prev->next = p->next; return dummy->next; }};

 

Leetcode: Remove Nth Node From End of List