Remove_Duplicates_from_Sorted_List.md

083. Remove Duplicates from Sorted List

Given a sorted linked list, delete all duplicates such that each element appear only once.

For example,

Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

Method:

similar as previous one:

# 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
        """
        dummy=ListNode(0)
        pre=dummy
        dummy.next=head
        while head and head.next:
            if head.next.val==head.val:
                while head.next and head.next.val==head.val:
                    head=head.next
                pre.next=head
            else:
                head=head.next
                pre=pre.next
        return dummy.next

using extra space:

# 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
        """
        dummy=ListNode(0)
        h=dummy
        l=[]
        while head:
            if head.val not in l:
                l.append(head.val)
            head=head.next
        for k in l:
            dummy.next=ListNode(k)
            dummy=dummy.next
        return h.next

Solution:

# 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
        """
        cur=head
        while cur and cur.next:
            if cur.next.val==cur.val:
                cur.next=cur.next.next
            else:
                cur=cur.next
        return head