| 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 node the zipper is focused on |
| 15 | path (list): The path of breadcrumbs leading to the current node |
| 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. |
| 24 | |
| 25 | Args: |
| 26 | tree (dict): A binary tree represented as a nested dictionary |
| 27 | with keys "value", "left", and "right" |
| 28 | |
| 29 | Returns: |
| 30 | Zipper: A new zipper focused on the root of the tree |
| 31 | |
| 32 | # Edge Case: Handle None tree input |
| 33 | """ |
| 34 | if tree is None: |
| 35 | return 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 stored in the focus node |
| 44 | |
| 45 | # Edge Case: Handle None node |
| 46 | """ |
| 47 | if self._node is None: |
| 48 | return None |
| 49 | return self._node["value"] |
| 50 | |
| 10 | 51 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 52 | """ |
| 53 | Set the value of the focus node, returning a new zipper. |
| 54 | |
| 55 | Args: |
| 56 | value (int): The new value to set |
| 57 | |
| 58 | Returns: |
| 59 | Zipper: A new zipper with the updated value |
| 60 | |
| 61 | # Edge Case: Handle None node |
| 62 | """ |
| 63 | if self._node is None: |
| 64 | return self |
| 65 | |
| 66 | new_node = { |
| 67 | "value": value, |
| 68 | "left": self._node["left"], |
| 69 | "right": self._node["right"] |
| 70 | } |
| 71 | return Zipper(new_node, self._path) |
| 72 | |
| 13 | 73 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 74 | """ |
| 75 | Move the focus to the left child of the current node. |
| 76 | |
| 77 | Returns: |
| 78 | Zipper | None: A new zipper focused on the left child, or None if no left child exists |
| 79 | |
| 80 | # Edge Case: Handle None node |
| 81 | # Edge Case: Handle missing left child |
| 82 | """ |
| 83 | if self._node is None or self._node["left"] is None: |
| 84 | return None |
| 85 | |
| 86 | # Create a breadcrumb to remember the path back |
| 87 | breadcrumb = { |
| 88 | "parent": self._node, |
| 89 | "side": "left", |
| 90 | "right": self._node["right"] |
| 91 | } |
| 92 | |
| 93 | return Zipper(self._node["left"], [breadcrumb] + self._path) |
| 94 | |
| 16 | 95 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 96 | """ |
| 97 | Set the left child of the focus node, returning a new zipper. |
| 98 | |
| 99 | Args: |
| 100 | tree (dict | None): The new left subtree |
| 101 | |
| 102 | Returns: |
| 103 | Zipper: A new zipper with the updated left child |
| 104 | |
| 105 | # Edge Case: Handle None node |
| 106 | """ |
| 107 | if self._node is None: |
| 108 | return self |
| 109 | |
| 110 | new_node = { |
| 111 | "value": self._node["value"], |
| 112 | "left": tree, |
| 113 | "right": self._node["right"] |
| 114 | } |
| 115 | return Zipper(new_node, self._path) |
| 116 | |
| 19 | 117 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 118 | """ |
| 119 | Move the focus to the right child of the current node. |
| 120 | |
| 121 | Returns: |
| 122 | Zipper | None: A new zipper focused on the right child, or None if no right child exists |
| 123 | |
| 124 | # Edge Case: Handle None node |
| 125 | # Edge Case: Handle missing right child |
| 126 | """ |
| 127 | if self._node is None or self._node["right"] is None: |
| 128 | return None |
| 129 | |
| 130 | # Create a breadcrumb to remember the path back |
| 131 | breadcrumb = { |
| 132 | "parent": self._node, |
| 133 | "side": "right", |
| 134 | "left": self._node["left"] |
| 135 | } |
| 136 | |
| 137 | return Zipper(self._node["right"], [breadcrumb] + self._path) |
| 138 | |
| 22 | 139 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 140 | """ |
| 141 | Set the right child of the focus node, returning a new zipper. |
| 142 | |
| 143 | Args: |
| 144 | tree (dict | None): The new right subtree |
| 145 | |
| 146 | Returns: |
| 147 | Zipper: A new zipper with the updated right child |
| 148 | |
| 149 | # Edge Case: Handle None node |
| 150 | """ |
| 151 | if self._node is None: |
| 152 | return self |
| 153 | |
| 154 | new_node = { |
| 155 | "value": self._node["value"], |
| 156 | "left": self._node["left"], |
| 157 | "right": tree |
| 158 | } |
| 159 | return Zipper(new_node, self._path) |
| 160 | |
| 25 | 161 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 162 | """ |
| 163 | Move the focus to the parent of the current node. |
| 164 | |
| 165 | Returns: |
| 166 | Zipper | None: A new zipper focused on the parent, or None if at root |
| 167 | |
| 168 | # Edge Case: Handle already at root (empty path) |
| 169 | """ |
| 170 | if not self._path: |
| 171 | return None |
| 172 | |
| 173 | breadcrumb = self._path[0] |
| 174 | parent = breadcrumb["parent"].copy() |
| 175 | |
| 176 | # Reconstruct the parent with the current node in the correct position |
| 177 | if breadcrumb["side"] == "left": |
| 178 | parent["left"] = self._node |
| 179 | parent["right"] = breadcrumb["right"] |
| 180 | else: # breadcrumb["side"] == "right" |
| 181 | parent["left"] = breadcrumb["left"] |
| 182 | parent["right"] = self._node |
| 183 | |
| 184 | return Zipper(parent, self._path[1:]) |
| 185 | |
| 28 | 186 | def to_tree(self) -> dict: |
| 29 | | pass |
| 187 | """ |
| 188 | Get the complete tree from the root. |
| 189 | |
| 190 | Returns: |
| 191 | dict: The complete binary tree as a nested dictionary |
| 192 | |
| 193 | # Edge Case: Handle None node |
| 194 | """ |
| 195 | if self._node is None: |
| 196 | return None |
| 197 | |
| 198 | # Navigate up to the root to get the complete tree |
| 199 | zipper = self |
| 200 | while zipper._path: |
| 201 | zipper = zipper.up() |
| 202 | return zipper._node |
| 203 | |
| 204 | # Handled Edge Cases: None tree input, None node, missing left child, missing right child, already at root |