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| 1 | +from __future__ import annotations |
| 2 | + |
| 3 | +from dataclasses import dataclass |
| 4 | + |
| 5 | + |
| 6 | +@dataclass |
| 7 | +class Node: |
| 8 | + data: int |
| 9 | + next_node: Node | None = None |
| 10 | + |
| 11 | + |
| 12 | +def print_linked_list(head: Node | None) -> None: |
| 13 | + """ |
| 14 | + Print the entire linked list iteratively. |
| 15 | + |
| 16 | + This function prints the elements of a linked list separated by '->'. |
| 17 | + |
| 18 | + Parameters: |
| 19 | + head (Node | None): The head of the linked list to be printed, |
| 20 | + or None if the linked list is empty. |
| 21 | + |
| 22 | + >>> head = insert_node(None, 0) |
| 23 | + >>> head = insert_node(head, 2) |
| 24 | + >>> head = insert_node(head, 1) |
| 25 | + >>> print_linked_list(head) |
| 26 | + 0->2->1 |
| 27 | + >>> head = insert_node(head, 4) |
| 28 | + >>> head = insert_node(head, 5) |
| 29 | + >>> print_linked_list(head) |
| 30 | + 0->2->1->4->5 |
| 31 | + """ |
| 32 | + if head is None: |
| 33 | + return |
| 34 | + while head.next_node is not None: |
| 35 | + print(head.data, end="->") |
| 36 | + head = head.next_node |
| 37 | + print(head.data) |
| 38 | + |
| 39 | + |
| 40 | +def insert_node(head: Node | None, data: int) -> Node: |
| 41 | + """ |
| 42 | + Insert a new node at the end of a linked list and return the new head. |
| 43 | + |
| 44 | + Parameters: |
| 45 | + head (Node | None): The head of the linked list. |
| 46 | + data (int): The data to be inserted into the new node. |
| 47 | + |
| 48 | + Returns: |
| 49 | + Node: The new head of the linked list. |
| 50 | + |
| 51 | + >>> head = insert_node(None, 10) |
| 52 | + >>> head = insert_node(head, 9) |
| 53 | + >>> head = insert_node(head, 8) |
| 54 | + >>> print_linked_list(head) |
| 55 | + 10->9->8 |
| 56 | + """ |
| 57 | + new_node = Node(data) |
| 58 | + # If the linked list is empty, the new_node becomes the head |
| 59 | + if head is None: |
| 60 | + return new_node |
| 61 | + |
| 62 | + temp_node = head |
| 63 | + while temp_node.next_node: |
| 64 | + temp_node = temp_node.next_node |
| 65 | + |
| 66 | + temp_node.next_node = new_node # type: ignore |
| 67 | + return head |
| 68 | + |
| 69 | + |
| 70 | +def rotate_to_the_right(head: Node, places: int) -> Node: |
| 71 | + """ |
| 72 | + Rotate a linked list to the right by places times. |
| 73 | + |
| 74 | + Parameters: |
| 75 | + head: The head of the linked list. |
| 76 | + places: The number of places to rotate. |
| 77 | + |
| 78 | + Returns: |
| 79 | + Node: The head of the rotated linked list. |
| 80 | + |
| 81 | + >>> rotate_to_the_right(None, places=1) |
| 82 | + Traceback (most recent call last): |
| 83 | + ... |
| 84 | + ValueError: The linked list is empty. |
| 85 | + >>> head = insert_node(None, 1) |
| 86 | + >>> rotate_to_the_right(head, places=1) == head |
| 87 | + True |
| 88 | + >>> head = insert_node(None, 1) |
| 89 | + >>> head = insert_node(head, 2) |
| 90 | + >>> head = insert_node(head, 3) |
| 91 | + >>> head = insert_node(head, 4) |
| 92 | + >>> head = insert_node(head, 5) |
| 93 | + >>> new_head = rotate_to_the_right(head, places=2) |
| 94 | + >>> print_linked_list(new_head) |
| 95 | + 4->5->1->2->3 |
| 96 | + """ |
| 97 | + # Check if the list is empty or has only one element |
| 98 | + if not head: |
| 99 | + raise ValueError("The linked list is empty.") |
| 100 | + |
| 101 | + if head.next_node is None: |
| 102 | + return head |
| 103 | + |
| 104 | + # Calculate the length of the linked list |
| 105 | + length = 1 |
| 106 | + temp_node = head |
| 107 | + while temp_node.next_node is not None: |
| 108 | + length += 1 |
| 109 | + temp_node = temp_node.next_node |
| 110 | + |
| 111 | + # Adjust the value of places to avoid places longer than the list. |
| 112 | + places %= length |
| 113 | + |
| 114 | + if places == 0: |
| 115 | + return head # As no rotation is needed. |
| 116 | + |
| 117 | + # Find the new head position after rotation. |
| 118 | + new_head_index = length - places |
| 119 | + |
| 120 | + # Traverse to the new head position |
| 121 | + temp_node = head |
| 122 | + for _ in range(new_head_index - 1): |
| 123 | + assert temp_node.next_node |
| 124 | + temp_node = temp_node.next_node |
| 125 | + |
| 126 | + # Update pointers to perform rotation |
| 127 | + assert temp_node.next_node |
| 128 | + new_head = temp_node.next_node |
| 129 | + temp_node.next_node = None |
| 130 | + temp_node = new_head |
| 131 | + while temp_node.next_node: |
| 132 | + temp_node = temp_node.next_node |
| 133 | + temp_node.next_node = head |
| 134 | + |
| 135 | + assert new_head |
| 136 | + return new_head |
| 137 | + |
| 138 | + |
| 139 | +if __name__ == "__main__": |
| 140 | + import doctest |
| 141 | + |
| 142 | + doctest.testmod() |
| 143 | + head = insert_node(None, 5) |
| 144 | + head = insert_node(head, 1) |
| 145 | + head = insert_node(head, 2) |
| 146 | + head = insert_node(head, 4) |
| 147 | + head = insert_node(head, 3) |
| 148 | + |
| 149 | + print("Original list: ", end="") |
| 150 | + print_linked_list(head) |
| 151 | + |
| 152 | + places = 3 |
| 153 | + new_head = rotate_to_the_right(head, places) |
| 154 | + |
| 155 | + print(f"After {places} iterations: ", end="") |
| 156 | + print_linked_list(new_head) |
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