leetcode第92题反转链表--头插法（迭代）_leetcode 头插法的题

反转链表就用头插法 

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def reverseBetween(self, head, left, right):
        """
        :type head: ListNode
        :type left: int
        :type right: int
        :rtype: ListNode
        """
        begin=cur=LN_head=ListNode()
        LN_head.next=head
        i=1
        while i<left:
            begin=begin.next
            i+=1
        end=begin.next
        for i in range(right-left):
            temp=end.next
            end.next=end.next.next
            temp.next=begin.next
            begin.next=temp
        return LN_head.next