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19. Remove Nth Node From End of List
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.
Note:
Given n will always be valid.
Follow up:
Could you do this in one pass?
解题分析
快慢指针
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/**
* Runtime: 0 ms, faster than 100.00% of Java online submissions for Remove Nth Node From End of List.
*
* Memory Usage: 34.6 MB, less than 100.00% of Java online submissions for Remove Nth Node From End of List.
*/
public ListNode removeNthFromEnd(ListNode head, int n) {
if (Objects.isNull(head) || n == 0) {
return head;
}
ListNode p1 = head;
int length = 1;
while (Objects.nonNull(p1.next) && length <= n) {
p1 = p1.next;
length++;
}
if (Objects.isNull(p1.next) && length == n) {
return head.next;
}
if (Objects.isNull(p1.next) && length < n) {
return head;
}
ListNode p2 = head;
while (Objects.nonNull(p1.next)) {
p1 = p1.next;
p2 = p2.next;
}
if (Objects.nonNull(p2.next)) {
p2.next = p2.next.next;
}
return head;
}