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