We have already discussed 2 different ways to clone a linked list. In this post, one more simple method to clone a linked list is discussed.
The idea is to use Hashing. Below is algorithm.
- Traverse the original linked list and make a copy in terms of data.
- Make a hash map of key value pair with original linked list node and copied linked list node.
- Traverse the original linked list again and using the hash map adjust the next and random reference of cloned linked list nodes.
Below is the implementation of above approach.
Python3
# Python3 program to clone a linked list # with random pointers class Node: def __init__(self, data): # Node Data self.data = data # Node Next self.next = None # Node Random self.random = None # Dictionary class MyDictionary(dict): # __init__ function def __init__(self): super().__init__() self = dict() # Function to add key:value def add(self, key, value): # Adding Values to dictionary self[key] = value # Linked list class class LinkedList: # Linked list constructor def __init__(self, node): self.head = node # Method to print the list. def __repr__(self): temp = self.head while temp is not None: random = temp.random random_data = (random.data if random is not None else -1) data = temp.data print(f"Data-{data}, Random data: {random_data}") temp = temp.next return "" # Push method to put data always at # the head in the linked list. def push(self, data): node = Node(data) node.next = self.head self.head = node # Actual clone method which returns head # reference of cloned linked list. def clone(self): # Initialize two references, one # with original list's head. original = self.head clone = None # Initialize two references, one # with original list's head. mp = MyDictionary() # Traverse the original list and # make a copy of that # in the clone linked list while original is not None: clone = Node(original.data) mp.add(original, clone) original = original.next # Adjusting the original # list reference again. original = self.head # Traversal of original list again # to adjust the next and random # references of clone list using hash map. while original is not None: clone = mp.get(original) clone.next = mp.get(original.next) clone.random = mp.get(original.random) original = original.next # Return the head reference of the clone list. return LinkedList(self.head) # Driver code # Pushing data in the linked list. l = LinkedList(Node(5)) l.push(4) l.push(3) l.push(2) l.push(1) # Setting up random references. l.head.random = l.head.next.nextl.head.next.random = l.head.next.next.nextl.head.next.next.random = l.head.next.next.next.nextl.head.next.next.next.random = (l.head.next.next.next.next.next) l.head.next.next.next.next.random = l.head.next # Making a clone of the # original linked list. clone = l.clone() # Print the original and cloned # linked list.s print("Original linked list") print(l) print("Cloned linked list") print(clone) # This code is contributed by ashwinathappan |
Output:
Original linked list Data = 1, Random data = 3 Data = 2, Random data = 4 Data = 3, Random data = 5 Data = 4, Random data = -1 Data = 5, Random data = 2 Cloned linked list Data = 1, Random data = 3 Data = 2, Random data = 4 Data = 3, Random data = 5 Data = 4, Random data = -1 Data = 5, Random data = 2
Time complexity: O(n)
Auxiliary space: O(n)
Please refer complete article on Clone a linked list with next and random pointer | Set 2 for more details!
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