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