博客域名：http://www.xnerv.wang
原题页面：https://oj.leetcode.com/problems/sort-list/
题目类型：
难度评价：★
本文地址：http://blog.csdn.net/nerv3x3/article/details/38143633
原题页面：https://oj.leetcode.com/problems/sort-list/
题目类型：
难度评价：★
本文地址：http://blog.csdn.net/nerv3x3/article/details/38143633
Sort a linked list in O(n log n) time using constant space complexity.
class Solution:
def findMiddle(self, head):
slow = head
fast = head.next
while None != fast and None != fast.next:
fast = fast.next.next
slow = slow.next
return slow
def mergeList(self, head):
if None == head.next:
return head
mid = self.findMiddle(head)
right_head = mid.next
mid.next = None
left_list = self.mergeList(head)
right_list = self.mergeList(right_head)
new_head = ListNode(-1)
new_tail = new_head
left_node = left_list
right_node = right_list
while None != left_node and None != right_node:
if left_node.val <= right_node.val:
new_tail.next = left_node
left_node = left_node.next
else:
new_tail.next = right_node
right_node = right_node.next
new_tail = new_tail.next
new_tail.next = left_node if None != left_node else right_node
return new_head.next
# @param head, a ListNode
# @return a ListNode
def sortList(self, head):
if None == head: # leetcode will input this !
return None
return self.mergeList(head)