“Связанный список в Merge Sort Python” Ответ

Связанный список в Merge Sort Python

# Python3 program to merge sort of linked list
 
# create Node using class Node.
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
 
class LinkedList:
    def __init__(self):
        self.head = None
     
    # push new value to linked list
    # using append method
    def append(self, new_value):
         
        # Allocate new node
        new_node = Node(new_value)
         
        # if head is None, initialize it to new node
        if self.head is None:
            self.head = new_node
            return
        curr_node = self.head
        while curr_node.next is not None:
            curr_node = curr_node.next
             
        # Append the new node at the end
        # of the linked list
        curr_node.next = new_node
         
    def sortedMerge(self, a, b):
        result = None
         
        # Base cases
        if a == None:
            return b
        if b == None:
            return a
             
        # pick either a or b and recur..
        if a.data <= b.data:
            result = a
            result.next = self.sortedMerge(a.next, b)
        else:
            result = b
            result.next = self.sortedMerge(a, b.next)
        return result
     
    def mergeSort(self, h):
         
        # Base case if head is None
        if h == None or h.next == None:
            return h
 
        # get the middle of the list
        middle = self.getMiddle(h)
        nexttomiddle = middle.next
 
        # set the next of middle node to None
        middle.next = None
 
        # Apply mergeSort on left list
        left = self.mergeSort(h)
         
        # Apply mergeSort on right list
        right = self.mergeSort(nexttomiddle)
 
        # Merge the left and right lists
        sortedlist = self.sortedMerge(left, right)
        return sortedlist
     
    # Utility function to get the middle
    # of the linked list
    def getMiddle(self, head):
        if (head == None):
            return head
 
        slow = head
        fast = head
 
        while (fast.next != None and
               fast.next.next != None):
            slow = slow.next
            fast = fast.next.next
             
        return slow
         
# Utility function to print the linked list
def printList(head):
    if head is None:
        print(' ')
        return
    curr_node = head
    while curr_node:
        print(curr_node.data, end = " ")
        curr_node = curr_node.next
    print(' ')
     
# Driver Code
if __name__ == '__main__':
    li = LinkedList()
     
    # Let us create a unsorted linked list
    # to test the functions created.
    # The list shall be a: 2->3->20->5->10->15
    li.append(15)
    li.append(10)
    li.append(5)
    li.append(20)
    li.append(3)
    li.append(2)
     
    # Apply merge Sort
    li.head = li.mergeSort(li.head)
    print ("Sorted Linked List is:")
    printList(li.head)
 
# This code is contributed by Vikas Chitturi