Remove Nth Node From End of List Problem
Description
LeetCode Problem 19.
Given the head of a linked list, remove the nth node from the end of the list and return its head.
Example 1:
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Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]
Example 2:
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Input: head = [1], n = 1
Output: []
Example 3:
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Input: head = [1,2], n = 1
Output: [1]
Constraints:
The number of nodes in the list is sz.
- 1 <= sz <= 30
- 0 <= Node.val <= 100
- 1 <= n <= sz
Sample C++ Code
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/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* removeNthFromEnd(ListNode* head, int n) {
if (head == NULL)
return NULL;
ListNode* first = head;
ListNode* second = new ListNode;
second->next = head;
int i = 1;
while (first != NULL) {
if (i > n) {
second = second->next;
}
first = first->next;
i ++;
}
if (second->next == head)
head = head->next;
else if (n > 1)
second->next = second->next->next;
else
second->next = NULL;
return head;
}
};