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19removeNthfromEofL.cpp
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19removeNthfromEofL.cpp
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//
//
//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.
//
/**
* 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)
{
if (head == NULL)
{
return NULL;
}
// write your code here
int len = 0;
ListNode *node = head;
while(node)
{
len++;
node = node->next;
}
if ( n > len )
{
return head;
}
ListNode *dummy = new ListNode(0);
dummy->next = head;
node = head; int index = n;
while(index>1)
{
node = node->next;
index--;
}
while(node->next)
{
node = node->next;
dummy = dummy->next;
}
if ( dummy->next == head)
{
ListNode *releasenode = head;
head = head->next;
delete releasenode;
delete dummy;
}
else
{
ListNode *releasenode = dummy->next;
dummy->next = dummy->next->next;
delete releasenode;
}
return head;
}
};