| 7 | |
| 8 | #class for Singly Linked List |
| 9 | class SinglyLinkedList(): |
| 10 | #constructor to initialise head and tail of a Singly Linked List. Iniltially set to None |
| 11 | def __init__(self): |
| 12 | self.head = self.tail = None |
| 13 | |
| 14 | #method to check if the List is empty |
| 15 | def isEmpty(self): |
| 16 | if (self.head == self.tail == None): |
| 17 | return True |
| 18 | return False |
| 19 | |
| 20 | #method to count thee no. of nodes in the list |
| 21 | def count(self): |
| 22 | if self.isEmpty(): |
| 23 | return 0 |
| 24 | n = 0 |
| 25 | temp = self.head |
| 26 | while (temp != None): |
| 27 | n += 1 |
| 28 | temp = temp.next |
| 29 | return n |
| 30 | |
| 31 | #method to add an element in the front i.e. head |
| 32 | def addFront(self, x): |
| 33 | new_node = Node(x) |
| 34 | if (self.isEmpty()): |
| 35 | self.head = self.tail = new_node |
| 36 | return |
| 37 | new_node.next = self.head |
| 38 | self.head = new_node |
| 39 | |
| 40 | #method to add element in the last i.e. tail |
| 41 | def addTail(self, x): |
| 42 | new_node = Node(x) |
| 43 | if (self.isEmpty()): |
| 44 | self.head = self.tail = new_node |
| 45 | return |
| 46 | self.tail.next = new_node |
| 47 | self.tail = new_node |
| 48 | |
| 49 | #method to insert an element at a specific position |
| 50 | def insert(self, x, pos): |
| 51 | if pos == 1: |
| 52 | self.addFront(x) |
| 53 | return |
| 54 | if pos == (self.count()+1): |
| 55 | self.addTail(x) |
| 56 | return |
| 57 | new_node = Node(x) |
| 58 | temp = self.head |
| 59 | i = 1 |
| 60 | while (temp != None) and (i < pos-1): |
| 61 | temp = temp.next |
| 62 | i += 1 |
| 63 | if (temp == None): |
| 64 | return |
| 65 | new_node.next = temp.next |
| 66 | temp.next = new_node |