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