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leetcode 019

admin 11月 13, 2020 0

Remove Nth Node From End of List
Method
Python code

Remove Nth Node From End of List

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.

Method

Put a root node, point to the head. Use two node, firstly move the first one for n times, then move together, if the first one reach to None, the second one jump.

Python code

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def removeNthFromEnd(self, head, n):
        """
        :type head: ListNode
        :type n: int
        :rtype: ListNode
        """
        dummy = ListNode(0)
        dummy.next = head
        p1 = p2 = dummy
        for i in range(n):
            p1 = p1.next
        while p1.next:
            p1 = p1.next
            p2 = p2.next
        p2.next = p2.next.next
        return dummy.next