This is a Python program to interchange two nodes in a linked list.
The program creates a single linked list and allows the user to interchange two nodes in the list.
1. Create a class Node with instance variables data and next.
2. Create a class LinkedList with instance variables head and last_node.
3. The variable head points to the first element in the linked list while last_node points to the last.
4. Define methods get_node, get_prev_node, append and display.
5. get_node takes an index as argument and traverses the list from the first node that many times to return the node at that index.
6. get_prev_node takes a reference node as argument and returns the previous node.
7. The method display traverses the list from the first node and prints the data of each node.
8. The method append appends a node with the data item passed to the end of the list.
9. Define the function interchange which takes a linked list and two indices n and m as arguments.
10. The function interchange interchanges the nodes at indices n and m.
11. Create an instance of LinkedList, append data to it and perform the exchange operation.
Here is the source code of a Python program to exchange two elements in a linked list. The program output is shown below.
class Node: def __init__(self, data): self.data = data self.next = None class LinkedList: def __init__(self): self.head = None self.last_node = None def append(self, data): if self.last_node is None: self.head = Node(data) self.last_node = self.head else: self.last_node.next = Node(data) self.last_node = self.last_node.next def display(self): current = self.head while current: print(current.data, end = ' ') current = current.next def get_node(self, index): current = self.head for i in range(index): if current is None: return None current = current.next return current def get_prev_node(self, ref_node): current = self.head while (current and current.next != ref_node): current = current.next return current def interchange(llist, n, m): node1 = llist.get_node(n) node2 = llist.get_node(m) prev_node1 = llist.get_prev_node(node1) prev_node2 = llist.get_prev_node(node2) if prev_node1 is not None: prev_node1.next = node2 else: llist.head = node2 if prev_node2 is not None: prev_node2.next = node1 else: llist.head = node1 temp = node2.next node2.next = node1.next node1.next = temp a_llist = LinkedList() data_list = input('Please enter the elements in the linked list: ').split() for data in data_list: a_llist.append(int(data)) ans = input('Please enter the two indices of the two elements that' ' you want to exchange: ').split() n = int(ans) m = int(ans) interchange(a_llist, n, m) print('The new list: ') a_llist.display()
1. An instance of LinkedList is created.
2. The user is prompted to enter the data items for the list.
3. The user is asked to enter n and m, the indices of the nodes which will be interchanged.
4. The function interchange is called to perform the exchange operation.
5. The linked list is displayed.
Case 1: Please enter the elements in the linked list: 1 2 Please enter the two indices of the two elements that you want to exchange: 0 1 The new list: 2 1 Case 2: Please enter the elements in the linked list: 4 5 1 Please enter the two indices of the two elements that you want to exchange: 1 2 The new list: 4 1 5 Case 3: Please enter the elements in the linked list: 3 1 30 4 5 10 23 Please enter the two indices of the two elements that you want to exchange: 2 5 The new list: 3 1 10 4 5 30 23
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