| 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 | navigation to parent and child nodes, as well as modification of the tree. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, path): |
| 10 | """ |
| 11 | Initialize a Zipper. |
| 12 | |
| 13 | Args: |
| 14 | tree (dict): The complete tree structure |
| 15 | path (list): Path from root to focus node, with context at each level |
| 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. |
| 24 | |
| 25 | Args: |
| 26 | tree (dict): A binary tree with keys "value", "left", and "right" |
| 27 | |
| 28 | Returns: |
| 29 | Zipper: A new zipper focused on the root of the tree |
| 30 | """ |
| 31 | # Edge Case: Handle None tree |
| 32 | if tree is None: |
| 33 | return None |
| 34 | return Zipper(tree, []) |
| 35 | |
| 36 | def _get_focus(self): |
| 37 | """ |
| 38 | Get the current focus node based on the path. |
| 39 | |
| 40 | Returns: |
| 41 | dict: The focus node |
| 42 | """ |
| 43 | node = self.tree |
| 44 | for direction, parent 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 | focus = self._get_focus() |
| 62 | # Edge Case: Handle None focus |
| 63 | if focus is None: |
| 64 | raise Exception("Focus 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. |
| 70 | |
| 71 | Args: |
| 72 | value (int): The new value for the focus node |
| 73 | |
| 74 | Returns: |
| 75 | Zipper: A new zipper with the updated value |
| 76 | """ |
| 77 | # Edge Case: Handle empty path (root node) |
| 78 | if not self.path: |
| 79 | new_tree = {'value': value, 'left': self.tree['left'], 'right': self.tree['right']} |
| 80 | return Zipper(new_tree, self.path) |
| 81 | |
| 82 | # Create a copy of the tree and path |
| 83 | new_tree = self._copy_tree() |
| 84 | new_path = list(self.path) |
| 85 | |
| 86 | # Navigate to the parent of the focus node |
| 87 | node = new_tree |
| 88 | for direction, parent in new_path[:-1]: |
| 89 | if direction == 'left': |
| 90 | node = node['left'] |
| 91 | else: # direction == 'right' |
| 92 | node = node['right'] |
| 93 | |
| 94 | # Update the value of the focus node |
| 95 | if new_path[-1][0] == 'left': |
| 96 | node['left'] = {'value': value, 'left': node['left']['left'] if node['left'] else None, |
| 97 | 'right': node['left']['right'] if node['left'] else None} |
| 98 | else: # direction == 'right' |
| 99 | node['right'] = {'value': value, 'left': node['right']['left'] if node['right'] else None, |
| 100 | 'right': node['right']['right'] if node['right'] else None} |
| 101 | |
| 102 | return Zipper(new_tree, new_path) |
| 103 | |
| 13 | 104 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 105 | """ |
| 106 | Move the focus to the left child of the current focus node. |
| 107 | |
| 108 | Returns: |
| 109 | Zipper | None: A new zipper focused on the left child, or None if no left child exists |
| 110 | """ |
| 111 | focus = self._get_focus() |
| 112 | # Edge Case: Handle None focus |
| 113 | if focus is None or focus['left'] is None: |
| 114 | return None |
| 115 | |
| 116 | # Create a new path entry for moving to the left child |
| 117 | new_path = list(self.path) |
| 118 | new_path.append(('left', {'value': focus['value'], 'right': focus['right']})) |
| 119 | |
| 120 | return Zipper(self.tree, new_path) |
| 121 | |
| 16 | 122 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 123 | """ |
| 124 | Set the left child of the focus node. |
| 125 | |
| 126 | Args: |
| 127 | tree (dict | None): The new left subtree |
| 128 | |
| 129 | Returns: |
| 130 | Zipper: A new zipper with the updated left child |
| 131 | """ |
| 132 | # Edge Case: Handle empty path (root node) |
| 133 | if not self.path: |
| 134 | new_tree = {'value': self.tree['value'], 'left': tree, 'right': self.tree['right']} |
| 135 | return Zipper(new_tree, self.path) |
| 136 | |
| 137 | # Create a copy of the tree and path |
| 138 | new_tree = self._copy_tree() |
| 139 | new_path = list(self.path) |
| 140 | |
| 141 | # Navigate to the parent of the focus node |
| 142 | node = new_tree |
| 143 | for direction, parent in new_path[:-1]: |
| 144 | if direction == 'left': |
| 145 | node = node['left'] |
| 146 | else: # direction == 'right' |
| 147 | node = node['right'] |
| 148 | |
| 149 | # Update the left child of the focus node |
| 150 | if new_path[-1][0] == 'left': |
| 151 | node['left'] = {'value': node['left']['value'], 'left': tree, |
| 152 | 'right': node['left']['right'] if node['left'] else None} |
| 153 | else: # direction == 'right' |
| 154 | node['right'] = {'value': node['right']['value'], 'left': tree, |
| 155 | 'right': node['right']['right'] if node['right'] else None} |
| 156 | |
| 157 | return Zipper(new_tree, new_path) |
| 158 | |
| 19 | 159 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 160 | """ |
| 161 | Move the focus to the right child of the current focus node. |
| 162 | |
| 163 | Returns: |
| 164 | Zipper | None: A new zipper focused on the right child, or None if no right child exists |
| 165 | """ |
| 166 | focus = self._get_focus() |
| 167 | # Edge Case: Handle None focus |
| 168 | if focus is None or focus['right'] is None: |
| 169 | return None |
| 170 | |
| 171 | # Create a new path entry for moving to the right child |
| 172 | new_path = list(self.path) |
| 173 | new_path.append(('right', {'value': focus['value'], 'left': focus['left']})) |
| 174 | |
| 175 | return Zipper(self.tree, new_path) |
| 176 | |
| 22 | 177 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 178 | """ |
| 179 | Set the right child of the focus node. |
| 180 | |
| 181 | Args: |
| 182 | tree (dict | None): The new right subtree |
| 183 | |
| 184 | Returns: |
| 185 | Zipper: A new zipper with the updated right child |
| 186 | """ |
| 187 | # Edge Case: Handle empty path (root node) |
| 188 | if not self.path: |
| 189 | new_tree = {'value': self.tree['value'], 'left': self.tree['left'], 'right': tree} |
| 190 | return Zipper(new_tree, self.path) |
| 191 | |
| 192 | # Create a copy of the tree and path |
| 193 | new_tree = self._copy_tree() |
| 194 | new_path = list(self.path) |
| 195 | |
| 196 | # Navigate to the parent of the focus node |
| 197 | node = new_tree |
| 198 | for direction, parent in new_path[:-1]: |
| 199 | if direction == 'left': |
| 200 | node = node['left'] |
| 201 | else: # direction == 'right' |
| 202 | node = node['right'] |
| 203 | |
| 204 | # Update the right child of the focus node |
| 205 | if new_path[-1][0] == 'left': |
| 206 | node['left'] = {'value': node['left']['value'], 'left': node['left']['left'] if node['left'] else None, |
| 207 | 'right': tree} |
| 208 | else: # direction == 'right' |
| 209 | node['right'] = {'value': node['right']['value'], 'left': node['right']['left'] if node['right'] else None, |
| 210 | 'right': tree} |
| 211 | |
| 212 | return Zipper(new_tree, new_path) |
| 213 | |
| 25 | 214 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 215 | """ |
| 216 | Move the focus to the parent of the current focus node. |
| 217 | |
| 218 | Returns: |
| 219 | Zipper | None: A new zipper focused on the parent, or None if at the root |
| 220 | """ |
| 221 | # Edge Case: Handle already at root |
| 222 | if not self.path: |
| 223 | return None |
| 224 | |
| 225 | # Create a new path without the last element |
| 226 | new_path = list(self.path[:-1]) |
| 227 | |
| 228 | return Zipper(self.tree, new_path) |
| 229 | |
| 28 | 230 | def to_tree(self) -> dict: |
| 29 | | pass |
| 231 | """ |
| 232 | Get the complete tree from the zipper. |
| 233 | |
| 234 | Returns: |
| 235 | dict: The complete binary tree |
| 236 | """ |
| 237 | return self.tree |
| 238 | |
| 239 | def _copy_tree(self): |
| 240 | """ |
| 241 | Create a deep copy of the tree. |
| 242 | |
| 243 | Returns: |
| 244 | dict: A deep copy of the tree |
| 245 | """ |
| 246 | def copy_node(node): |
| 247 | if node is None: |
| 248 | return None |
| 249 | return { |
| 250 | 'value': node['value'], |
| 251 | 'left': copy_node(node['left']), |
| 252 | 'right': copy_node(node['right']) |
| 253 | } |
| 254 | |
| 255 | return copy_node(self.tree) |
| 256 | |
| 257 | # Handled Edge Cases: None tree, None focus, empty path (root node), no left child, no right child, already at root |