| 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 | A zipper contains a data structure and a pointer (focus) into that structure. |
| 6 | It supports moving through the tree and modifying it in a functional way. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, path=None): |
| 10 | """ |
| 11 | Initialize a Zipper. |
| 12 | |
| 13 | Args: |
| 14 | tree (dict): The binary tree represented as a dict with keys 'value', 'left', 'right' |
| 15 | path (list): A list of tuples representing the path from root to focus node |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.path = path or [] |
| 19 | |
| 3 | 20 | @staticmethod |
| 4 | 21 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 22 | """ |
| 23 | Create a zipper from a binary tree. |
| 24 | |
| 25 | Args: |
| 26 | tree (dict): The binary tree with keys 'value', 'left', 'right' |
| 27 | |
| 6 | 28 | |
| 29 | Returns: |
| 30 | Zipper: A new zipper focused on the root of the tree |
| 31 | """ |
| 32 | # Edge Case: Handle None tree input |
| 33 | if tree is None: |
| 34 | return None |
| 35 | return Zipper(tree) |
| 36 | |
| 37 | def _get_focus_node(self): |
| 38 | """ |
| 39 | Get the current focus node by traversing the path. |
| 40 | |
| 41 | |
| 42 | Returns: |
| 43 | dict: The focus node |
| 44 | """ |
| 45 | node = self.tree |
| 46 | for direction, parent in self.path: |
| 47 | if direction == 'left': |
| 48 | node = node['left'] |
| 49 | else: # direction == 'right' |
| 50 | node = node['right'] |
| 51 | return node |
| 52 | |
| 7 | 53 | def value(self) -> int: |
| 8 | | pass |
| 54 | """ |
| 55 | Get the value of the focus node. |
| 56 | |
| 9 | 57 | |
| 58 | Returns: |
| 59 | int: The value of the focus node |
| 60 | """ |
| 61 | # Edge Case: Handle None tree |
| 62 | if self.tree is None: |
| 63 | return None |
| 64 | return self._get_focus_node()['value'] |
| 65 | |
| 10 | 66 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 67 | """ |
| 68 | Set the value of the focus node, returning a new zipper. |
| 69 | |
| 70 | Args: |
| 71 | value (int): The new value |
| 72 | |
| 12 | 73 | |
| 74 | Returns: |
| 75 | Zipper: A new zipper with the updated value |
| 76 | """ |
| 77 | # Edge Case: Handle None tree |
| 78 | if self.tree is None: |
| 79 | return self |
| 80 | |
| 81 | # Create a deep copy of the tree |
| 82 | new_tree = self._deep_copy_tree(self.tree) |
| 83 | |
| 84 | # Navigate to the focus node in the new tree and update its value |
| 85 | node = new_tree |
| 86 | for direction, parent in self.path: |
| 87 | if direction == 'left': |
| 88 | node = node['left'] |
| 89 | else: # direction == 'right' |
| 90 | node = node['right'] |
| 91 | |
| 92 | node['value'] = value |
| 93 | |
| 94 | return Zipper(new_tree, list(self.path)) |
| 95 | |
| 13 | 96 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 97 | """ |
| 98 | Move the focus to the left child of the current node. |
| 99 | |
| 15 | 100 | |
| 101 | Returns: |
| 102 | Zipper | None: A new zipper focused on the left child, or None if no left child |
| 103 | """ |
| 104 | # Edge Case: Handle None tree |
| 105 | if self.tree is None: |
| 106 | return None |
| 107 | |
| 108 | focus_node = self._get_focus_node() |
| 109 | |
| 110 | # Edge Case: Handle None left child |
| 111 | if focus_node['left'] is None: |
| 112 | return None |
| 113 | |
| 114 | # Create a new path entry for moving to the left child |
| 115 | new_path = list(self.path) |
| 116 | new_path.append(('left', focus_node)) |
| 117 | |
| 118 | return Zipper(self.tree, new_path) |
| 119 | |
| 16 | 120 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 121 | """ |
| 122 | Set the left child of the focus node, returning a new zipper. |
| 123 | |
| 124 | Args: |
| 125 | tree (dict | None): The new left subtree |
| 126 | |
| 18 | 127 | |
| 128 | Returns: |
| 129 | Zipper: A new zipper with the updated left child |
| 130 | """ |
| 131 | # Edge Case: Handle None tree |
| 132 | if self.tree is None: |
| 133 | return self |
| 134 | |
| 135 | # Create a deep copy of the tree |
| 136 | new_tree = self._deep_copy_tree(self.tree) |
| 137 | |
| 138 | # Navigate to the focus node in the new tree and update its left child |
| 139 | node = new_tree |
| 140 | for direction, parent in self.path: |
| 141 | if direction == 'left': |
| 142 | node = node['left'] |
| 143 | else: # direction == 'right' |
| 144 | node = node['right'] |
| 145 | |
| 146 | node['left'] = tree |
| 147 | |
| 148 | return Zipper(new_tree, list(self.path)) |
| 149 | |
| 19 | 150 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 151 | """ |
| 152 | Move the focus to the right child of the current node. |
| 153 | |
| 21 | 154 | |
| 155 | Returns: |
| 156 | Zipper | None: A new zipper focused on the right child, or None if no right child |
| 157 | """ |
| 158 | # Edge Case: Handle None tree |
| 159 | if self.tree is None: |
| 160 | return None |
| 161 | |
| 162 | focus_node = self._get_focus_node() |
| 163 | |
| 164 | # Edge Case: Handle None right child |
| 165 | if focus_node['right'] is None: |
| 166 | return None |
| 167 | |
| 168 | # Create a new path entry for moving to the right child |
| 169 | new_path = list(self.path) |
| 170 | new_path.append(('right', focus_node)) |
| 171 | |
| 172 | return Zipper(self.tree, new_path) |
| 173 | |
| 22 | 174 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 175 | """ |
| 176 | Set the right child of the focus node, returning a new zipper. |
| 177 | |
| 178 | Args: |
| 179 | tree (dict | None): The new right subtree |
| 180 | |
| 24 | 181 | |
| 182 | Returns: |
| 183 | Zipper: A new zipper with the updated right child |
| 184 | """ |
| 185 | # Edge Case: Handle None tree |
| 186 | if self.tree is None: |
| 187 | return self |
| 188 | |
| 189 | # Create a deep copy of the tree |
| 190 | new_tree = self._deep_copy_tree(self.tree) |
| 191 | |
| 192 | # Navigate to the focus node in the new tree and update its right child |
| 193 | node = new_tree |
| 194 | for direction, parent in self.path: |
| 195 | if direction == 'left': |
| 196 | node = node['left'] |
| 197 | else: # direction == 'right' |
| 198 | node = node['right'] |
| 199 | |
| 200 | node['right'] = tree |
| 201 | |
| 202 | return Zipper(new_tree, list(self.path)) |
| 203 | |
| 25 | 204 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 205 | """ |
| 206 | Move the focus to the parent of the current node. |
| 207 | |
| 27 | 208 | |
| 209 | Returns: |
| 210 | Zipper | None: A new zipper focused on the parent, or None if at root |
| 211 | """ |
| 212 | # Edge Case: Handle None tree |
| 213 | if self.tree is None: |
| 214 | return None |
| 215 | |
| 216 | # Edge Case: Handle already at root (empty path) |
| 217 | if not self.path: |
| 218 | return None |
| 219 | |
| 220 | # Create a new path without the last element |
| 221 | new_path = list(self.path[:-1]) |
| 222 | |
| 223 | return Zipper(self.tree, new_path) |
| 224 | |
| 28 | 225 | def to_tree(self) -> dict: |
| 29 | | pass |
| 226 | """ |
| 227 | Get the complete tree from the zipper. |
| 228 | |
| 229 | |
| 230 | Returns: |
| 231 | dict: The complete binary tree |
| 232 | """ |
| 233 | # Edge Case: Handle None tree |
| 234 | if self.tree is None: |
| 235 | return None |
| 236 | return self.tree |
| 237 | |
| 238 | def _deep_copy_tree(self, tree): |
| 239 | """ |
| 240 | Create a deep copy of a binary tree. |
| 241 | |
| 242 | Args: |
| 243 | tree (dict): The tree to copy |
| 244 | |
| 245 | |
| 246 | Returns: |
| 247 | dict: A deep copy of the tree |
| 248 | """ |
| 249 | if tree is None: |
| 250 | return None |
| 251 | |
| 252 | return { |
| 253 | 'value': tree['value'], |
| 254 | 'left': self._deep_copy_tree(tree['left']), |
| 255 | 'right': self._deep_copy_tree(tree['right']) |
| 256 | } |
| 257 | # Handled Edge Cases: None tree input, None left child, None right child, already at root |