Given a linked list, remove the n-th node from the end of list and return its head.
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.
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 || head->next == NULL){
return NULL;
}
ListNode * firstNode = head;
ListNode * secondNode = head;
for(int i = 0;i < n; i++){
firstNode = firstNode->next;
}
//1,2,3,4,5 n = 4
if(firstNode == NULL){
return head->next;
}
while(firstNode->next != NULL)
{
firstNode = firstNode->next;
secondNode = secondNode->next;
}
secondNode->next = secondNode->next->next;
return head;
}
};
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
if( head == null || head.next == null){
return null;
}
ListNode firstNode = head;
ListNode secondNode = head;
for(int i = 0; i < n; i++){
firstNode = firstNode.next;
}
//1,2,3,4,5 n = 4
if(firstNode == null){
return head.next;
}
while(firstNode.next != null)
{
firstNode = firstNode.next;
secondNode = secondNode.next;
}
secondNode.next = secondNode.next.next;
return head;
}
}
'''
class ListNode:
def __init__(self, value):
self.value = value
self.next = None
'''
def del_node_reverse_k(node, k):
if not node or k <= 0:
return
head1 = node
for _ in range(k):
if not head1:
return
head1 = head1.next
if head1 == None:
node = node.next
return node
head2 = node
while head1.next:
head1 = head1.next
pre = head2
head2 = head2.next
head2.next = head2.next.next
return node