leetcode: 19. Remove Nth Node From End of List

Problem

# 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.

AC

class ListNode():    def __init__(self, x):        self.val = x        self.next = Noneclass Solution():    def removeNthFromEnd(self, head, x):        slow = fast = dummy = ListNode(0)        dummy.next = head        while x and fast.next:            fast, x = fast.next, x - 1        while fast.next:            slow, fast = slow.next, fast.next        slow.next = slow.next.next        return dummy.nextif __name__ == "__main__":    head, head.next, head.next.next, head.next.next.next, head.next.next.next.next \        = ListNode(1), ListNode(2), ListNode(3), ListNode(4), ListNode(5)    result = Solution().removeNthFromEnd(head, 2)    assert '{0}->{1}->{2}->{3}'.format(result.val, result.next.val, result.next.next.val, result.next.next.next.val) \           == '1->2->3->5'