| 1 | 1 | class Zipper: |
| 2 | | # Tree is a dict with keys "value" (int), "left" (dict or None), "right" (dict or None) |
| 2 | """ |
| 3 | A zipper for navigating and manipulating a binary tree. |
| 4 | |
| 5 | The zipper maintains a focus on a specific node in the tree and allows |
| 6 | traversal and modification operations while preserving the tree structure. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, path): |
| 10 | """ |
| 11 | Initialize a Zipper instance. |
| 12 | |
| 13 | Args: |
| 14 | tree (dict): The full tree structure |
| 15 | path (list): Path from root to current focus node, each element is a tuple (parent_node, direction) |
| 16 | """ |
| 17 | self._tree = tree |
| 18 | self._path = path |
| 19 | |
| 3 | 20 | @staticmethod |
| 4 | 21 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 22 | """ |
| 23 | Create a zipper from a binary tree with focus on the root node. |
| 24 | |
| 25 | Args: |
| 26 | tree (dict): A binary tree represented as nested dictionaries with keys 'value', 'left', 'right' |
| 27 | |
| 28 | Returns: |
| 29 | Zipper: A new zipper instance focused on the root of the tree |
| 30 | """ |
| 31 | # Edge Case: Handle None tree input |
| 32 | if tree is None: |
| 33 | return None |
| 34 | return Zipper(tree, []) |
| 35 | |
| 36 | def _get_focus_node(self): |
| 37 | """ |
| 38 | Get the current focus node based on the path. |
| 39 | |
| 40 | Returns: |
| 41 | dict: The current focus node |
| 42 | """ |
| 43 | node = self._tree |
| 44 | for parent, direction in self._path: |
| 45 | if direction == 'left': |
| 46 | node = node['left'] |
| 47 | else: # direction == 'right' |
| 48 | node = node['right'] |
| 49 | return node |
| 50 | |
| 7 | 51 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 52 | """ |
| 53 | Get the value of the focus node. |
| 54 | |
| 55 | Returns: |
| 56 | int: The value of the focus node |
| 57 | |
| 58 | Raises: |
| 59 | Exception: If the focus node is None |
| 60 | """ |
| 61 | # Edge Case: Handle when focus node is None |
| 62 | focus = self._get_focus_node() |
| 63 | if focus is None: |
| 64 | raise Exception("Focus node is None") |
| 65 | return focus['value'] |
| 66 | |
| 10 | 67 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 68 | """ |
| 69 | Set the value of the focus node, returning a new zipper. |
| 70 | |
| 71 | Args: |
| 72 | value (int): The new value for the focus node |
| 73 | |
| 74 | Returns: |
| 75 | Zipper: A new zipper with updated focus node value |
| 76 | """ |
| 77 | # Edge Case: Handle when focus node is None |
| 78 | if not self._path and self._tree is None: |
| 79 | new_tree = {'value': value, 'left': None, 'right': None} |
| 80 | return Zipper(new_tree, []) |
| 81 | |
| 82 | # Create a deep copy of the tree |
| 83 | new_tree = self._deep_copy_tree(self._tree) |
| 84 | |
| 85 | # Navigate to the focus node in the copied tree and update its value |
| 86 | node = new_tree |
| 87 | for parent, direction in self._path: |
| 88 | if direction == 'left': |
| 89 | node = node['left'] |
| 90 | else: # direction == 'right' |
| 91 | node = node['right'] |
| 92 | node['value'] = value |
| 93 | |
| 94 | return Zipper(new_tree, self._path[:]) |
| 95 | |
| 13 | 96 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 97 | """ |
| 98 | Move the focus to the left child of the current focus node. |
| 99 | |
| 100 | Returns: |
| 101 | Zipper | None: A new zipper focused on the left child, or None if no left child exists |
| 102 | """ |
| 103 | focus = self._get_focus_node() |
| 104 | # Edge Case: Handle when focus node is None |
| 105 | if focus is None: |
| 106 | return None |
| 107 | # Edge Case: Handle when left child is None |
| 108 | if focus['left'] is None: |
| 109 | return None |
| 110 | |
| 111 | new_path = self._path + [(focus, 'left')] |
| 112 | return Zipper(self._tree, new_path) |
| 113 | |
| 16 | 114 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 115 | """ |
| 116 | Set the left child of the focus node, returning a new zipper. |
| 117 | |
| 118 | Args: |
| 119 | tree (dict | None): The new left subtree |
| 120 | |
| 121 | Returns: |
| 122 | Zipper: A new zipper with updated left child |
| 123 | """ |
| 124 | # Edge Case: Handle when focus node is None |
| 125 | if not self._path and self._tree is None: |
| 126 | # If we're at the root and it's None, create a new tree |
| 127 | new_tree = {'value': 0, 'left': tree, 'right': None} # Default value of 0 |
| 128 | return Zipper(new_tree, []) |
| 129 | |
| 130 | # Create a deep copy of the tree |
| 131 | new_tree = self._deep_copy_tree(self._tree) |
| 132 | |
| 133 | # Navigate to the focus node in the copied tree and update its left child |
| 134 | node = new_tree |
| 135 | for parent, direction in self._path: |
| 136 | if direction == 'left': |
| 137 | node = node['left'] |
| 138 | else: # direction == 'right' |
| 139 | node = node['right'] |
| 140 | node['left'] = tree |
| 141 | |
| 142 | return Zipper(new_tree, self._path[:]) |
| 143 | |
| 19 | 144 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 145 | """ |
| 146 | Move the focus to the right child of the current focus node. |
| 147 | |
| 148 | Returns: |
| 149 | Zipper | None: A new zipper focused on the right child, or None if no right child exists |
| 150 | """ |
| 151 | focus = self._get_focus_node() |
| 152 | # Edge Case: Handle when focus node is None |
| 153 | if focus is None: |
| 154 | return None |
| 155 | # Edge Case: Handle when right child is None |
| 156 | if focus['right'] is None: |
| 157 | return None |
| 158 | |
| 159 | new_path = self._path + [(focus, 'right')] |
| 160 | return Zipper(self._tree, new_path) |
| 161 | |
| 22 | 162 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 163 | """ |
| 164 | Set the right child of the focus node, returning a new zipper. |
| 165 | |
| 166 | Args: |
| 167 | tree (dict | None): The new right subtree |
| 168 | |
| 169 | Returns: |
| 170 | Zipper: A new zipper with updated right child |
| 171 | """ |
| 172 | # Edge Case: Handle when focus node is None |
| 173 | if not self._path and self._tree is None: |
| 174 | # If we're at the root and it's None, create a new tree |
| 175 | new_tree = {'value': 0, 'left': None, 'right': tree} # Default value of 0 |
| 176 | return Zipper(new_tree, []) |
| 177 | |
| 178 | # Create a deep copy of the tree |
| 179 | new_tree = self._deep_copy_tree(self._tree) |
| 180 | |
| 181 | # Navigate to the focus node in the copied tree and update its right child |
| 182 | node = new_tree |
| 183 | for parent, direction in self._path: |
| 184 | if direction == 'left': |
| 185 | node = node['left'] |
| 186 | else: # direction == 'right' |
| 187 | node = node['right'] |
| 188 | node['right'] = tree |
| 189 | |
| 190 | return Zipper(new_tree, self._path[:]) |
| 191 | |
| 25 | 192 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 193 | """ |
| 194 | Move the focus to the parent of the current focus node. |
| 195 | |
| 196 | Returns: |
| 197 | Zipper | None: A new zipper focused on the parent, or None if already at root |
| 198 | """ |
| 199 | # Edge Case: Handle when already at root |
| 200 | if not self._path: |
| 201 | return None |
| 202 | |
| 203 | new_path = self._path[:-1] |
| 204 | return Zipper(self._tree, new_path) |
| 205 | |
| 28 | 206 | def to_tree(self) -> dict: |
| 29 | | pass |
| 207 | """ |
| 208 | Get the complete tree from the zipper. |
| 209 | |
| 210 | Returns: |
| 211 | dict: The complete binary tree |
| 212 | """ |
| 213 | return self._tree |
| 214 | |
| 215 | def _deep_copy_tree(self, tree): |
| 216 | """ |
| 217 | Create a deep copy of a binary tree. |
| 218 | |
| 219 | Args: |
| 220 | tree (dict): The tree to copy |
| 221 | |
| 222 | Returns: |
| 223 | dict: A deep copy of the tree |
| 224 | """ |
| 225 | if tree is None: |
| 226 | return None |
| 227 | |
| 228 | return { |
| 229 | 'value': tree['value'], |
| 230 | 'left': self._deep_copy_tree(tree['left']), |
| 231 | 'right': self._deep_copy_tree(tree['right']) |
| 232 | } |
| 233 | # Handled Edge Cases: None tree input, focus node is None, left child is None, right child is None, already at root |