leetcode 83. 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.

# 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
        """
        node = head
        while node:
            tmp = node
            val = node.val            
            while node.next and node.next.val == val:
                node = node.next
            # assert node.next is None or node.next.val != val
            tmp.next = node.next
            node = node.next
        return head

 

# 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 = cur = ListNode(None)
        node = head
        while node:
            if node.val != cur.val:
                cur.next = node
                cur = cur.next
            node = node.next
        cur.next = None
        return dummy.next

 

發現其餘人的解法和個人都不同，每次上一個節點比較，若是數值相同，則直接刪除當前節點。

# 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      
        node = head
        while node.next:
            if node.next.val == node.val:
                node.next = node.next.next
            else:
                node = node.next
        return head

 遞歸解法：

# 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              
        if not head.next: return head        
        head.next = self.deleteDuplicates(head.next)
        if head.val == head.next.val:
            return head.next
        else:
            return head