| 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 maintains a focus on a specific node in the tree and allows |
| 6 | navigation 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 tree structure being navigated. |
| 15 | path (list): A list of breadcrumbs representing the path from root to focus. |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.path = path |
| 19 | |
| 20 | # Calculate the current focus based on the path |
| 21 | self.focus = tree |
| 22 | for breadcrumb in self.path: |
| 23 | direction, parent_value, left_subtree, right_subtree = breadcrumb |
| 24 | if direction == 'left': |
| 25 | self.focus = self.focus['left'] |
| 26 | else: # direction == 'right' |
| 27 | self.focus = self.focus['right'] |
| 28 | |
| 3 | 29 | @staticmethod |
| 4 | 30 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 31 | """ |
| 32 | Create a zipper from a binary tree, with focus on the root node. |
| 33 | |
| 34 | Args: |
| 35 | tree (dict): A binary tree represented as a nested dictionary. |
| 36 | |
| 37 | Returns: |
| 38 | Zipper: A new zipper instance focused on the root of the tree. |
| 39 | """ |
| 40 | # Edge Case: Handle None tree input |
| 41 | if tree is None: |
| 42 | return None |
| 43 | return Zipper(tree, []) |
| 44 | |
| 7 | 45 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 46 | """ |
| 47 | Get the value of the focus node. |
| 48 | |
| 49 | Returns: |
| 50 | int: The value stored in the focus node. |
| 51 | """ |
| 52 | # Edge Case: Handle None focus |
| 53 | if self.focus is None: |
| 54 | return None |
| 55 | return self.focus['value'] |
| 56 | |
| 10 | 57 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 58 | """ |
| 59 | Set the value of the focus node, returning a new zipper. |
| 60 | |
| 61 | Args: |
| 62 | value (int): The new value to set. |
| 63 | |
| 64 | Returns: |
| 65 | Zipper: A new zipper with the updated value. |
| 66 | """ |
| 67 | # Edge Case: Handle None focus |
| 68 | if self.focus is None: |
| 69 | return self |
| 70 | |
| 71 | # Create a deep copy of the tree |
| 72 | new_tree = self._deep_copy_tree(self.tree) |
| 73 | |
| 74 | # Navigate to the focus position in the new tree |
| 75 | current = new_tree |
| 12 | 76 | |
| 77 | # Edge Case: Handle empty path (focus is root) |
| 78 | if not self.path: |
| 79 | current['value'] = value |
| 80 | else: |
| 81 | for breadcrumb in self.path: |
| 82 | direction, parent_value, left_subtree, right_subtree = breadcrumb |
| 83 | if direction == 'left': |
| 84 | current = current['left'] |
| 85 | else: # direction == 'right' |
| 86 | current = current['right'] |
| 87 | current['value'] = value |
| 88 | |
| 89 | return Zipper(new_tree, self.path) |
| 90 | |
| 13 | 91 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 92 | """ |
| 93 | Move the focus to the left child of the current node. |
| 94 | |
| 95 | Returns: |
| 96 | Zipper | None: A new zipper focused on the left child, or None if no left child exists. |
| 97 | """ |
| 98 | # Edge Case: Handle None focus |
| 99 | if self.focus is None or self.focus['left'] is None: |
| 100 | return None |
| 101 | |
| 102 | # Create a breadcrumb for the current node |
| 103 | breadcrumb = ('left', self.focus['value'], self.focus['left'], self.focus['right']) |
| 104 | |
| 105 | # Return a new zipper with updated path |
| 106 | return Zipper(self.tree, self.path + [breadcrumb]) |
| 107 | |
| 16 | 108 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 109 | """ |
| 110 | Set the left subtree of the focus node, returning a new zipper. |
| 111 | |
| 112 | Args: |
| 113 | tree (dict | None): The new left subtree. |
| 114 | |
| 115 | Returns: |
| 116 | Zipper: A new zipper with the updated left subtree. |
| 117 | """ |
| 118 | # Edge Case: Handle None focus |
| 119 | if self.focus is None: |
| 120 | return self |
| 121 | |
| 122 | # Create a deep copy of the tree |
| 123 | new_tree = self._deep_copy_tree(self.tree) |
| 124 | |
| 125 | # Navigate to the focus position in the new tree |
| 126 | current = new_tree |
| 18 | 127 | |
| 128 | # Edge Case: Handle empty path (focus is root) |
| 129 | if not self.path: |
| 130 | current['left'] = tree |
| 131 | else: |
| 132 | for breadcrumb in self.path: |
| 133 | direction, parent_value, left_subtree, right_subtree = breadcrumb |
| 134 | if direction == 'left': |
| 135 | current = current['left'] |
| 136 | else: # direction == 'right' |
| 137 | current = current['right'] |
| 138 | current['left'] = tree |
| 139 | |
| 140 | return Zipper(new_tree, self.path) |
| 141 | |
| 19 | 142 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 143 | """ |
| 144 | Move the focus to the right child of the current node. |
| 145 | |
| 146 | Returns: |
| 147 | Zipper | None: A new zipper focused on the right child, or None if no right child exists. |
| 148 | """ |
| 149 | # Edge Case: Handle None focus |
| 150 | if self.focus is None or self.focus['right'] is None: |
| 151 | return None |
| 152 | |
| 153 | # Create a breadcrumb for the current node |
| 154 | breadcrumb = ('right', self.focus['value'], self.focus['left'], self.focus['right']) |
| 155 | |
| 156 | # Return a new zipper with updated path |
| 157 | return Zipper(self.tree, self.path + [breadcrumb]) |
| 158 | |
| 22 | 159 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 160 | """ |
| 161 | Set the right subtree of the focus node, returning a new zipper. |
| 162 | |
| 163 | Args: |
| 164 | tree (dict | None): The new right subtree. |
| 165 | |
| 166 | Returns: |
| 167 | Zipper: A new zipper with the updated right subtree. |
| 168 | """ |
| 169 | # Edge Case: Handle None focus |
| 170 | if self.focus is None: |
| 171 | return self |
| 172 | |
| 173 | # Create a deep copy of the tree |
| 174 | new_tree = self._deep_copy_tree(self.tree) |
| 175 | |
| 176 | # Navigate to the focus position in the new tree |
| 177 | current = new_tree |
| 24 | 178 | |
| 179 | # Edge Case: Handle empty path (focus is root) |
| 180 | if not self.path: |
| 181 | current['right'] = tree |
| 182 | else: |
| 183 | for breadcrumb in self.path: |
| 184 | direction, parent_value, left_subtree, right_subtree = breadcrumb |
| 185 | if direction == 'left': |
| 186 | current = current['left'] |
| 187 | else: # direction == 'right' |
| 188 | current = current['right'] |
| 189 | current['right'] = tree |
| 190 | |
| 191 | return Zipper(new_tree, self.path) |
| 192 | |
| 25 | 193 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 194 | """ |
| 195 | Move the focus to the parent of the current node. |
| 196 | |
| 197 | Returns: |
| 198 | Zipper | None: A new zipper focused on the parent, or None if already at root. |
| 199 | """ |
| 200 | # Edge Case: Handle already at root (empty path) |
| 201 | if not self.path: |
| 202 | return None |
| 203 | |
| 204 | # Remove the last breadcrumb to move up |
| 205 | new_path = self.path[:-1] |
| 206 | return Zipper(self.tree, new_path) |
| 207 | |
| 28 | 208 | def to_tree(self) -> dict: |
| 29 | | pass |
| 209 | """ |
| 210 | Get the complete tree from the zipper. |
| 211 | |
| 212 | Returns: |
| 213 | dict: The complete binary tree. |
| 214 | """ |
| 215 | return self.tree |
| 216 | |
| 217 | def _deep_copy_tree(self, tree): |
| 218 | """ |
| 219 | Create a deep copy of a tree structure. |
| 220 | |
| 221 | Args: |
| 222 | tree (dict): The tree to copy. |
| 223 | |
| 224 | Returns: |
| 225 | dict: A deep copy of the tree. |
| 226 | """ |
| 227 | # Edge Case: Handle None tree |
| 228 | if tree is None: |
| 229 | return None |
| 230 | |
| 231 | # Edge Case: Handle leaf node |
| 232 | if 'value' not in tree: |
| 233 | return tree |
| 234 | |
| 235 | return { |
| 236 | 'value': tree['value'], |
| 237 | 'left': self._deep_copy_tree(tree['left']), |
| 238 | 'right': self._deep_copy_tree(tree['right']) |
| 239 | } |
| 240 | |
| 241 | # Handled Edge Cases: None tree input, None focus, empty path (focus is root), already at root |