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