链表_leetcode86

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

class Solution(object):
 def partition(self, head, x):
 """
 :type head: ListNode
 :type x: int
 :rtype: ListNode
 """

 if not head or not head.next:
 return head

 if x < 1:
 return head

 cur = head
 count = 1

 while cur and count < x:
 cur = cur.next
 count += 1

 if count < x :
 return head

 xNode = cur

 cur = head
 leftNode = None
 rightNode = None

 left = None
 right = None

 while cur :

 if cur.val < xNode.val and leftNode == None:
 leftNode =cur
 left = leftNode

 if cur.val >= xNode.val and rightNode == None:
 rightNode = cur
 right = rightNode


 if cur.val < xNode.val:
 left.next = cur
 left = cur

 else:
 right.next = cur
 right = cur

 cur = cur.next

 left.next = rightNode

 return leftNode


class Solution2(object):
 def partition(self, head, x):
 """
 :type head: ListNode
 :type x: int
 :rtype: ListNode
 """

 if head is None or head.next is None or x is None:
 return head

 p1 = head1 = ListNode(0)
 p2 = head2 = ListNode(0)
 p = head

 while p:
 if p.val < x:
 p1.next = p
 p1 = p1.next
 else:
 p2.next = p
 p2 = p2.next
 p = p.next
 p1.next = head2.next
 p2.next = None


 return head1.next