Leetcode 147. Insertion Sort List

https://leetcode.com/problems/insertion-sort-list/

It is a linked list version of insert sorting.

Solution:

# T:O(n^2) S:O(1)
class Solution:
# @param head, a ListNode
# @return a ListNode
    def insertionSortList(self, head):
        if not head:
            return head
        dummy = ListNode(0)
        dummy.next = head
        curr = head
        while curr.next:
            if curr.next.val < curr.val:
                pre = dummy 
                while pre.next.val < curr.next.val:
                    pre = pre.next
                tmp = curr.next
                curr.next = tmp.next
                tmp.next = pre.next
                pre.next = tmp
            else:
                curr = curr.next
        return dummy.next

Run Time: 348 ms