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