82.py

'''
Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

Example 1:

Input: 1->2->3->3->4->4->5
Output: 1->2->5
Example 2:

Input: 1->1->1->2->3
Output: 2->3
'''

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

class Solution(object):
    def deleteDuplicates(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if not head:
        	return None

        result = ListNode(0)
        ans = result
        curr = head
        while curr:
        	value = curr.val
        	count = 0
        	while curr and curr.val == value:
        		curr = curr.next
        		count += 1
        	if count == 1:
        		result.next = ListNode(value)
        		result = result.next
        return ans.next