| 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 a binary tree that allows navigation and manipulation. |
| 4 | |
| 5 | The zipper maintains a focus on a specific node in the tree and allows |
| 6 | movement through the tree structure while keeping track of the path taken. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree: dict, path: list = None): |
| 10 | """ |
| 11 | Initialize a Zipper with a tree and optional path. |
| 12 | |
| 13 | Args: |
| 14 | tree: The binary tree represented as a dict with keys 'value', 'left', 'right' |
| 15 | path: A list of tuples tracking the path to the current focus |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.path = path or [] |
| 19 | |
| 3 | 20 | @staticmethod |
| 4 | 21 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 22 | """ |
| 23 | Create a zipper from a binary tree with focus on the root node. |
| 24 | |
| 25 | Args: |
| 26 | tree: The binary tree represented as a dict with keys 'value', 'left', 'right' |
| 27 | |
| 28 | |
| 29 | Returns: |
| 30 | A new Zipper instance focused on the root of the tree |
| 31 | """ |
| 32 | # Edge Case: Handle None tree input |
| 33 | if tree is None: |
| 34 | return None |
| 35 | return Zipper(tree) |
| 6 | 36 | |
| 7 | 37 | def value(self) -> int: |
| 8 | | pass |
| 38 | """ |
| 39 | Get the value of the focus node. |
| 40 | |
| 41 | |
| 42 | Returns: |
| 43 | The value of the current focus node |
| 44 | """ |
| 45 | current = self.tree |
| 46 | for direction, parent in self.path: |
| 47 | if direction == 'left': |
| 48 | current = current['left'] |
| 49 | else: # direction == 'right' |
| 50 | current = current['right'] |
| 51 | return current['value'] |
| 9 | 52 | |
| 10 | 53 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 54 | """ |
| 55 | Set the value of the focus node and return a new zipper. |
| 56 | |
| 57 | Args: |
| 58 | value: The new value for the focus node |
| 59 | |
| 60 | |
| 61 | Returns: |
| 62 | A new Zipper instance with the updated value |
| 63 | """ |
| 64 | # Edge Case: Handle None value input |
| 65 | if value is None: |
| 66 | raise ValueError("Value cannot be None") |
| 67 | |
| 68 | new_tree = self._copy_tree(self.tree) |
| 69 | current = new_tree |
| 70 | |
| 71 | for direction, parent in self.path: |
| 72 | if direction == 'left': |
| 73 | current = current['left'] |
| 74 | else: # direction == 'right' |
| 75 | current = current['right'] |
| 76 | |
| 77 | current['value'] = value |
| 78 | return Zipper(new_tree, self.path.copy()) |
| 12 | 79 | |
| 13 | 80 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 81 | """ |
| 82 | Move the focus to the left child of the current node. |
| 83 | |
| 84 | |
| 85 | Returns: |
| 86 | A new Zipper focused on the left child, or None if no left child exists |
| 87 | """ |
| 88 | current = self.tree |
| 89 | for direction, parent in self.path: |
| 90 | if direction == 'left': |
| 91 | current = current['left'] |
| 92 | else: # direction == 'right' |
| 93 | current = current['right'] |
| 94 | |
| 95 | # Edge Case: Handle case where current node has no left child |
| 96 | if current['left'] is None: |
| 97 | return None |
| 98 | |
| 99 | new_path = self.path.copy() |
| 100 | new_path.append(('left', current)) |
| 101 | return Zipper(self.tree, new_path) |
| 15 | 102 | |
| 16 | 103 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 104 | """ |
| 105 | Set the left child of the focus node and return a new zipper. |
| 106 | |
| 107 | Args: |
| 108 | tree: The new left subtree (or None to remove the left child) |
| 109 | |
| 110 | |
| 111 | Returns: |
| 112 | A new Zipper instance with the updated left child |
| 113 | """ |
| 114 | new_tree = self._copy_tree(self.tree) |
| 115 | current = new_tree |
| 116 | |
| 117 | for direction, parent in self.path: |
| 118 | if direction == 'left': |
| 119 | current = current['left'] |
| 120 | else: # direction == 'right' |
| 121 | current = current['right'] |
| 122 | |
| 123 | current['left'] = tree |
| 124 | return Zipper(new_tree, self.path.copy()) |
| 18 | 125 | |
| 19 | 126 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 127 | """ |
| 128 | Move the focus to the right child of the current node. |
| 129 | |
| 130 | |
| 131 | Returns: |
| 132 | A new Zipper focused on the right child, or None if no right child exists |
| 133 | """ |
| 134 | current = self.tree |
| 135 | for direction, parent in self.path: |
| 136 | if direction == 'left': |
| 137 | current = current['left'] |
| 138 | else: # direction == 'right' |
| 139 | current = current['right'] |
| 140 | |
| 141 | # Edge Case: Handle case where current node has no right child |
| 142 | if current['right'] is None: |
| 143 | return None |
| 144 | |
| 145 | new_path = self.path.copy() |
| 146 | new_path.append(('right', current)) |
| 147 | return Zipper(self.tree, new_path) |
| 21 | 148 | |
| 22 | 149 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 150 | """ |
| 151 | Set the right child of the focus node and return a new zipper. |
| 152 | |
| 153 | Args: |
| 154 | tree: The new right subtree (or None to remove the right child) |
| 155 | |
| 156 | |
| 157 | Returns: |
| 158 | A new Zipper instance with the updated right child |
| 159 | """ |
| 160 | new_tree = self._copy_tree(self.tree) |
| 161 | current = new_tree |
| 162 | |
| 163 | for direction, parent in self.path: |
| 164 | if direction == 'left': |
| 165 | current = current['left'] |
| 166 | else: # direction == 'right' |
| 167 | current = current['right'] |
| 168 | |
| 169 | current['right'] = tree |
| 170 | return Zipper(new_tree, self.path.copy()) |
| 24 | 171 | |
| 25 | 172 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 173 | """ |
| 174 | Move the focus to the parent of the current node. |
| 175 | |
| 176 | |
| 177 | Returns: |
| 178 | A new Zipper focused on the parent node, or None if already at root |
| 179 | """ |
| 180 | # Edge Case: Handle case where we're already at the root (no parent) |
| 181 | if not self.path: |
| 182 | return None |
| 183 | |
| 184 | new_path = self.path.copy() |
| 185 | new_path.pop() |
| 186 | return Zipper(self.tree, new_path) |
| 27 | 187 | |
| 28 | 188 | def to_tree(self) -> dict: |
| 29 | | pass |
| 189 | """ |
| 190 | Get the complete tree from the zipper. |
| 191 | |
| 192 | |
| 193 | Returns: |
| 194 | The complete binary tree as a dict |
| 195 | """ |
| 196 | return self.tree |
| 197 | |
| 198 | def _copy_tree(self, tree: dict) -> dict: |
| 199 | """ |
| 200 | Create a deep copy of a binary tree. |
| 201 | |
| 202 | Args: |
| 203 | tree: The tree to copy |
| 204 | |
| 205 | |
| 206 | Returns: |
| 207 | A deep copy of the tree |
| 208 | """ |
| 209 | if tree is None: |
| 210 | return None |
| 211 | |
| 212 | return { |
| 213 | 'value': tree['value'], |
| 214 | 'left': self._copy_tree(tree['left']), |
| 215 | 'right': self._copy_tree(tree['right']) |
| 216 | } |
| 217 | # Handled Edge Cases: None tree input, None value input, no left child, no right child, already at root |