Selection Sort Linked List

Given a singly-linked list, where each node contains an integer value, sort it in ascending order. The selectoin sort algorithm should be used to solve this problem.

Examples

null, is sorted to null
1 -> null, is sorted to 1 -> null
1 -> 2 -> 3 -> null, is sorted to 1 -> 2 -> 3 -> null
4 -> 2 -> 6 -> -3 -> 5 -> null, is sorted to 2 -> 3 -> 4 -> 5 -> 6

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

class Solution(object):  
  def selectionSort(self, head):
    if head is None:
      return None
    dummy = ListNode(0)
    dummy.next = head
    min_node = ListNode(None)
    while head is not None:
      min_node = self.find_min(head)
      self.swap_val(head,min_node)
      head = head.next
    return dummy.next
    
    """
    input: ListNode head
    return: ListNode
    """
    # write your solution here  
    
  def find_min(self,head):
    min_node = ListNode(500)
    while head is not None:
      if head.val < min_node.val:
        min_node = head
      head = head.next
    return min_node
  
  def swap_val(self,node1,node2):
    node1.val,node2.val = node2.val,node1.val