| 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 and modification operations while preserving the tree structure. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, node, path): |
| 10 | """ |
| 11 | Initialize a Zipper instance. |
| 12 | |
| 13 | Args: |
| 14 | node (dict): The current focus node with keys 'value', 'left', 'right' |
| 15 | path (list): List of breadcrumbs representing the path from root to focus |
| 16 | """ |
| 17 | self._node = node |
| 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 |
| 27 | |
| 28 | Returns: |
| 29 | Zipper: A new zipper instance focused on the root of the tree |
| 30 | |
| 31 | Edge Case: Empty tree (None) - Returns a zipper with None node and empty path |
| 32 | """ |
| 33 | # Edge Case: Empty tree |
| 34 | if tree is None: |
| 35 | return Zipper(None, []) |
| 36 | return Zipper(tree, []) |
| 37 | |
| 7 | 38 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 39 | """ |
| 40 | Get the value of the focus node. |
| 41 | |
| 42 | Returns: |
| 43 | int: The value of the focus node |
| 44 | |
| 45 | Edge Case: Focus node is None - Raises AttributeError |
| 46 | """ |
| 47 | # Edge Case: Focus node is None |
| 48 | if self._node is None: |
| 49 | raise AttributeError("Cannot get value of None node") |
| 50 | return self._node["value"] |
| 51 | |
| 10 | 52 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 53 | """ |
| 54 | Set the value of the focus node, returning a new zipper. |
| 55 | |
| 56 | Args: |
| 57 | value (int): The new value for the focus node |
| 58 | |
| 59 | Returns: |
| 60 | Zipper: A new zipper with updated focus node value |
| 61 | |
| 62 | Edge Case: Focus node is None - Returns a new zipper with None node |
| 63 | """ |
| 64 | # Edge Case: Focus node is None |
| 65 | if self._node is None: |
| 66 | return Zipper(None, self._path) |
| 67 | |
| 68 | new_node = { |
| 69 | "value": value, |
| 70 | "left": self._node["left"], |
| 71 | "right": self._node["right"] |
| 72 | } |
| 73 | return Zipper(new_node, self._path) |
| 74 | |
| 13 | 75 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 76 | """ |
| 77 | Move the focus to the left child of the current node. |
| 78 | |
| 79 | Returns: |
| 80 | Zipper | None: A new zipper focused on the left child, or None if no left child |
| 81 | |
| 82 | Edge Case: Focus node is None - Returns None |
| 83 | Edge Case: No left child - Returns None |
| 84 | """ |
| 85 | # Edge Case: Focus node is None |
| 86 | if self._node is None: |
| 87 | return None |
| 88 | |
| 89 | # Edge Case: No left child |
| 90 | if self._node["left"] is None: |
| 91 | return None |
| 92 | |
| 93 | # Create breadcrumb to store current node context |
| 94 | breadcrumb = { |
| 95 | "parent": { |
| 96 | "value": self._node["value"], |
| 97 | "right": self._node["right"] |
| 98 | }, |
| 99 | "is_left": True |
| 100 | } |
| 101 | |
| 102 | new_path = [breadcrumb] + self._path |
| 103 | return Zipper(self._node["left"], new_path) |
| 104 | |
| 16 | 105 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 106 | """ |
| 107 | Set the left child of the focus node, returning a new zipper. |
| 108 | |
| 109 | Args: |
| 110 | tree (dict | None): The new left subtree or None |
| 111 | |
| 112 | Returns: |
| 113 | Zipper: A new zipper with updated left child |
| 114 | |
| 115 | Edge Case: Focus node is None - Returns a new zipper with None node |
| 116 | """ |
| 117 | # Edge Case: Focus node is None |
| 118 | if self._node is None: |
| 119 | return Zipper(None, self._path) |
| 120 | |
| 121 | new_node = { |
| 122 | "value": self._node["value"], |
| 123 | "left": tree, |
| 124 | "right": self._node["right"] |
| 125 | } |
| 126 | return Zipper(new_node, self._path) |
| 127 | |
| 19 | 128 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 129 | """ |
| 130 | Move the focus to the right child of the current node. |
| 131 | |
| 132 | Returns: |
| 133 | Zipper | None: A new zipper focused on the right child, or None if no right child |
| 134 | |
| 135 | Edge Case: Focus node is None - Returns None |
| 136 | Edge Case: No right child - Returns None |
| 137 | """ |
| 138 | # Edge Case: Focus node is None |
| 139 | if self._node is None: |
| 140 | return None |
| 141 | |
| 142 | # Edge Case: No right child |
| 143 | if self._node["right"] is None: |
| 144 | return None |
| 145 | |
| 146 | # Create breadcrumb to store current node context |
| 147 | breadcrumb = { |
| 148 | "parent": { |
| 149 | "value": self._node["value"], |
| 150 | "left": self._node["left"] |
| 151 | }, |
| 152 | "is_left": False |
| 153 | } |
| 154 | |
| 155 | new_path = [breadcrumb] + self._path |
| 156 | return Zipper(self._node["right"], new_path) |
| 157 | |
| 22 | 158 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 159 | """ |
| 160 | Set the right child of the focus node, returning a new zipper. |
| 161 | |
| 162 | Args: |
| 163 | tree (dict | None): The new right subtree or None |
| 164 | |
| 165 | Returns: |
| 166 | Zipper: A new zipper with updated right child |
| 167 | |
| 168 | Edge Case: Focus node is None - Returns a new zipper with None node |
| 169 | """ |
| 170 | # Edge Case: Focus node is None |
| 171 | if self._node is None: |
| 172 | return Zipper(None, self._path) |
| 173 | |
| 174 | new_node = { |
| 175 | "value": self._node["value"], |
| 176 | "left": self._node["left"], |
| 177 | "right": tree |
| 178 | } |
| 179 | return Zipper(new_node, self._path) |
| 180 | |
| 25 | 181 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 182 | """ |
| 183 | Move the focus to the parent of the current node. |
| 184 | |
| 185 | Returns: |
| 186 | Zipper | None: A new zipper focused on the parent, or None if at root |
| 187 | |
| 188 | Edge Case: Already at root (empty path) - Returns None |
| 189 | Edge Case: Focus node is None - Returns None |
| 190 | """ |
| 191 | # Edge Case: Focus node is None or already at root |
| 192 | if self._node is None or not self._path: |
| 193 | return None |
| 194 | |
| 195 | # Get the top breadcrumb |
| 196 | breadcrumb = self._path[0] |
| 197 | rest_path = self._path[1:] |
| 198 | |
| 199 | parent = breadcrumb["parent"] |
| 200 | |
| 201 | # Reconstruct the parent node with the current node in the correct position |
| 202 | if breadcrumb["is_left"]: |
| 203 | # Current node was the left child |
| 204 | reconstructed_parent = { |
| 205 | "value": parent["value"], |
| 206 | "left": self._node, |
| 207 | "right": parent.get("right") |
| 208 | } |
| 209 | else: |
| 210 | # Current node was the right child |
| 211 | reconstructed_parent = { |
| 212 | "value": parent["value"], |
| 213 | "left": parent.get("left"), |
| 214 | "right": self._node |
| 215 | } |
| 216 | |
| 217 | return Zipper(reconstructed_parent, rest_path) |
| 218 | |
| 28 | 219 | def to_tree(self) -> dict: |
| 29 | | pass |
| 220 | """ |
| 221 | Convert the zipper back to a tree representation. |
| 222 | |
| 223 | Returns: |
| 224 | dict: The complete tree with all modifications applied |
| 225 | |
| 226 | Edge Case: Focus node is None - Reconstructs tree from path |
| 227 | """ |
| 228 | # Navigate back to the root to get the complete tree |
| 229 | current_zipper = self |
| 230 | |
| 231 | # Edge Case: Current zipper is already at root |
| 232 | if not self._path: |
| 233 | return self._node |
| 234 | |
| 235 | # Move up until we reach the root |
| 236 | while True: |
| 237 | up_zipper = current_zipper.up() |
| 238 | if up_zipper is None: |
| 239 | break |
| 240 | current_zipper = up_zipper |
| 241 | |
| 242 | return current_zipper._node |
| 243 | |
| 244 | # Handled Edge Cases: Empty tree in from_tree, None focus node in value, set_value, left, set_left, right, set_right, up, to_tree, No left child in left, No right child in right, Already at root in up |