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