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70 lines
1.3 KiB
Python
70 lines
1.3 KiB
Python
"""
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19. Remove Nth Node From End of List
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Difficulty: Medium
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https://leetcode.com/problems/remove-nth-node-from-end-of-list/
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──────────────────────────────────────────────────
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Given the head of a linked list, remove the n^th node from the end of
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the list and return its head.
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Example 1:
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Input: head = [1,2,3,4,5], n = 2
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Output: [1,2,3,5]
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Example 2:
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Input: head = [1], n = 1
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Output: []
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Example 3:
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Input: head = [1,2], n = 1
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Output: [1]
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Constraints:
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• The number of nodes in the list is sz.
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• 1 <= sz <= 30
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• 0 <= Node.val <= 100
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• 1 <= n <= sz
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Follow up: Could you do this in one pass?
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"""
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# Definition for singly-linked list.
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# class ListNode:
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# def __init__(self, val=0, next=None):
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# self.val = val
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# self.next = next
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class Solution:
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def removeNthFromEnd(self, head: ListNode | None, n: int) -> ListNode | None:
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dummy = ListNode(0)
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dummy.next = head
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fast = dummy
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for _ in range(n):
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if fast.next is None:
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return head
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fast = fast.next
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slow = dummy
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while fast.next is not None:
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slow = slow.next
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fast = fast.next
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slow.next = slow.next.next
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return dummy.next
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