| 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 | functional navigation and modification operations. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree: dict, path: list = None): |
| 10 | """ |
| 11 | Initialize a Zipper with a tree and an optional path to the focus node. |
| 12 | |
| 13 | Args: |
| 14 | tree: The binary tree represented as a dict with keys "value", "left", and "right" |
| 15 | path: A list of tuples representing the path to the focus node. Each tuple contains |
| 16 | the parent node and a string indicating if we went "left" or "right" |
| 17 | """ |
| 18 | self.tree = tree |
| 19 | self.path = path or [] |
| 20 | |
| 3 | 21 | @staticmethod |
| 4 | 22 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 23 | """ |
| 24 | Create a zipper from a binary tree, with focus on the root node. |
| 25 | |
| 26 | Args: |
| 27 | tree: The binary tree represented as a dict with keys "value", "left", and "right" |
| 28 | |
| 6 | 29 | |
| 30 | Returns: |
| 31 | A new Zipper instance focused on the root of the tree |
| 32 | """ |
| 33 | # Edge Case: Handle None tree input |
| 34 | if tree is None: |
| 35 | return None |
| 36 | return Zipper(tree) |
| 37 | |
| 7 | 38 | def value(self) -> int: |
| 8 | | pass |
| 39 | """ |
| 40 | Get the value of the focus node. |
| 41 | |
| 9 | 42 | |
| 43 | Returns: |
| 44 | The value of the focus node |
| 45 | """ |
| 46 | current = self._get_focus_node() |
| 47 | # Edge Case: Handle None focus node |
| 48 | if current is None: |
| 49 | return None |
| 50 | return current["value"] |
| 51 | |
| 10 | 52 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 53 | """ |
| 54 | Set the value of the focus node, returning a new zipper. |
| 55 | |
| 56 | Args: |
| 57 | value: The new value for the focus node |
| 58 | |
| 12 | 59 | |
| 60 | Returns: |
| 61 | A new Zipper instance with the updated value |
| 62 | """ |
| 63 | # Edge Case: Handle None tree |
| 64 | if self.tree is None: |
| 65 | return Zipper(None, self.path) |
| 66 | |
| 67 | new_tree = self._copy_tree() |
| 68 | focus_node = new_tree |
| 69 | |
| 70 | # Navigate to the focus node in the copied tree |
| 71 | for parent, direction in self.path: |
| 72 | if direction == "left": |
| 73 | focus_node = focus_node["left"] |
| 74 | else: # direction == "right" |
| 75 | focus_node = focus_node["right"] |
| 76 | |
| 77 | # Edge Case: Handle None focus node |
| 78 | if focus_node is None: |
| 79 | return Zipper(new_tree, self.path) |
| 80 | |
| 81 | focus_node["value"] = value |
| 82 | return Zipper(new_tree, self.path) |
| 83 | |
| 13 | 84 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 85 | """ |
| 86 | Move the focus to the left child of the current focus node. |
| 87 | |
| 15 | 88 | |
| 89 | Returns: |
| 90 | A new Zipper focused on the left child, or None if no left child exists |
| 91 | """ |
| 92 | current = self._get_focus_node() |
| 93 | # Edge Case: Handle None focus node |
| 94 | if current is None or current["left"] is None: |
| 95 | return None |
| 96 | |
| 97 | new_path = self.path + [(current, "left")] |
| 98 | return Zipper(self.tree, new_path) |
| 99 | |
| 16 | 100 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 101 | """ |
| 102 | Set the left child of the focus node, returning a new zipper. |
| 103 | |
| 104 | Args: |
| 105 | tree: The new left subtree (or None to remove the left child) |
| 106 | |
| 18 | 107 | |
| 108 | Returns: |
| 109 | A new Zipper instance with the updated left child |
| 110 | """ |
| 111 | # Edge Case: Handle None tree |
| 112 | if self.tree is None: |
| 113 | return Zipper(None, self.path) |
| 114 | |
| 115 | new_tree = self._copy_tree() |
| 116 | focus_node = new_tree |
| 117 | |
| 118 | # Navigate to the focus node in the copied tree |
| 119 | for parent, direction in self.path: |
| 120 | if direction == "left": |
| 121 | focus_node = focus_node["left"] |
| 122 | else: # direction == "right" |
| 123 | focus_node = focus_node["right"] |
| 124 | |
| 125 | # Edge Case: Handle None focus node |
| 126 | if focus_node is None: |
| 127 | return Zipper(new_tree, self.path) |
| 128 | |
| 129 | focus_node["left"] = tree |
| 130 | return Zipper(new_tree, self.path) |
| 131 | |
| 19 | 132 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 133 | """ |
| 134 | Move the focus to the right child of the current focus node. |
| 135 | |
| 21 | 136 | |
| 137 | Returns: |
| 138 | A new Zipper focused on the right child, or None if no right child exists |
| 139 | """ |
| 140 | current = self._get_focus_node() |
| 141 | # Edge Case: Handle None focus node |
| 142 | if current is None or current["right"] is None: |
| 143 | return None |
| 144 | |
| 145 | new_path = self.path + [(current, "right")] |
| 146 | return Zipper(self.tree, new_path) |
| 147 | |
| 22 | 148 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 149 | """ |
| 150 | Set the right child of the focus node, returning a new zipper. |
| 151 | |
| 152 | Args: |
| 153 | tree: The new right subtree (or None to remove the right child) |
| 154 | |
| 24 | 155 | |
| 156 | Returns: |
| 157 | A new Zipper instance with the updated right child |
| 158 | """ |
| 159 | # Edge Case: Handle None tree |
| 160 | if self.tree is None: |
| 161 | return Zipper(None, self.path) |
| 162 | |
| 163 | new_tree = self._copy_tree() |
| 164 | focus_node = new_tree |
| 165 | |
| 166 | # Navigate to the focus node in the copied tree |
| 167 | for parent, direction in self.path: |
| 168 | if direction == "left": |
| 169 | focus_node = focus_node["left"] |
| 170 | else: # direction == "right" |
| 171 | focus_node = focus_node["right"] |
| 172 | |
| 173 | # Edge Case: Handle None focus node |
| 174 | if focus_node is None: |
| 175 | return Zipper(new_tree, self.path) |
| 176 | |
| 177 | focus_node["right"] = tree |
| 178 | return Zipper(new_tree, self.path) |
| 179 | |
| 25 | 180 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 181 | """ |
| 182 | Move the focus to the parent of the current focus node. |
| 183 | |
| 27 | 184 | |
| 185 | Returns: |
| 186 | A new Zipper focused on the parent node, or None if already at the root |
| 187 | """ |
| 188 | # Edge Case: Handle already at root (empty path) |
| 189 | if not self.path: |
| 190 | return None |
| 191 | |
| 192 | new_path = self.path[:-1] |
| 193 | return Zipper(self.tree, new_path) |
| 194 | |
| 28 | 195 | def to_tree(self) -> dict: |
| 29 | | pass |
| 196 | """ |
| 197 | Get the complete tree from the zipper. |
| 198 | |
| 199 | |
| 200 | Returns: |
| 201 | The complete binary tree as a dict |
| 202 | """ |
| 203 | return self.tree |
| 204 | |
| 205 | def _get_focus_node(self) -> dict | None: |
| 206 | """ |
| 207 | Helper method to get the current focus node based on the path. |
| 208 | |
| 209 | |
| 210 | Returns: |
| 211 | The focus node or None if the path is invalid |
| 212 | """ |
| 213 | # Edge Case: Handle None tree |
| 214 | if self.tree is None: |
| 215 | return None |
| 216 | |
| 217 | node = self.tree |
| 218 | for parent, direction in self.path: |
| 219 | if node is None: |
| 220 | return None |
| 221 | if direction == "left": |
| 222 | node = node["left"] |
| 223 | else: # direction == "right" |
| 224 | node = node["right"] |
| 225 | return node |
| 226 | |
| 227 | def _copy_tree(self) -> dict: |
| 228 | """ |
| 229 | Helper method to create a deep copy of the tree. |
| 230 | |
| 231 | |
| 232 | Returns: |
| 233 | A deep copy of the tree |
| 234 | """ |
| 235 | def copy_node(node): |
| 236 | if node is None: |
| 237 | return None |
| 238 | return { |
| 239 | "value": node["value"], |
| 240 | "left": copy_node(node["left"]), |
| 241 | "right": copy_node(node["right"]) |
| 242 | } |
| 243 | |
| 244 | return copy_node(self.tree) |
| 245 | |
| 246 | # Handled Edge Cases: None tree input, None focus node, already at root, invalid path |