LintCode Python 简单级题目 112.删除链表中的重复元素

"""
Definition of ListNode
class ListNode(object):
    def __init__(self, val, next=None):
        self.val = val
        self.next = next
"""
class Solution:
    """
    @param head: A ListNode
    @return: A ListNode
    """
    def deleteDuplicates(self, head):
        # write your code here
        if head is None:
            return None
        pre = head
        cur = pre
        fol = pre.next
        while fol.next is not None:
            # 一直找到第一个与pre值不等的fol，删除中间所有重复元素
            if pre.val == fol.val:
                fol = fol.next
            else:
                pre.next = fol
                pre = fol
                fol = pre.next
        # 检测末尾是否相等
        if pre.val == fol.val:
            pre.next = fol.next
        else:
            pre.next = fol
        return cur