| 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 | A zipper maintains a focus on a specific node in the tree and allows |
| 6 | functional navigation and modification operations. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, path): |
| 10 | """ |
| 11 | Initialize a Zipper. |
| 12 | |
| 13 | Args: |
| 14 | tree: The full tree structure (dict with 'value', 'left', 'right') |
| 15 | path: List of breadcrumbs representing path from root to focus |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.path = path |
| 19 | # Current node is determined by following the path from root |
| 20 | self._current = self._get_current_node() |
| 21 | |
| 3 | 22 | @staticmethod |
| 4 | 23 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 24 | """ |
| 25 | Create a zipper from a binary tree. |
| 26 | |
| 27 | Args: |
| 28 | tree: A binary tree represented as a dict with keys 'value', 'left', 'right' |
| 29 | |
| 30 | Returns: |
| 31 | A new Zipper instance focused on the root node |
| 32 | """ |
| 33 | # Edge Case: Handle None tree |
| 34 | if tree is None: |
| 35 | return None |
| 36 | return Zipper(tree, []) |
| 37 | |
| 38 | def _get_current_node(self): |
| 39 | """ |
| 40 | Get the current node by following the path from the root. |
| 41 | |
| 42 | Returns: |
| 43 | The current node dict |
| 44 | """ |
| 45 | # Edge Case: Handle empty path (focus is root) |
| 46 | if not self.path: |
| 47 | return self.tree |
| 48 | |
| 49 | node = self.tree |
| 50 | for direction, parent in self.path: |
| 51 | if direction == 'left': |
| 52 | node = node['left'] |
| 53 | else: # direction == 'right' |
| 54 | node = node['right'] |
| 55 | return node |
| 56 | |
| 7 | 57 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 58 | """ |
| 59 | Get the value of the focus node. |
| 60 | |
| 61 | Returns: |
| 62 | The value of the current node |
| 63 | """ |
| 64 | # Edge Case: Handle None current node |
| 65 | if self._current is None: |
| 66 | return None |
| 67 | return self._current['value'] |
| 68 | |
| 10 | 69 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 70 | """ |
| 71 | Set the value of the focus node. |
| 72 | |
| 73 | Args: |
| 74 | value: The new value for the focus node |
| 75 | |
| 76 | Returns: |
| 77 | A new Zipper with the updated value |
| 78 | """ |
| 79 | # Edge Case: Handle None current node |
| 80 | if self._current is None: |
| 81 | return self |
| 82 | |
| 83 | # Create a deep copy of the tree |
| 84 | new_tree = self._deep_copy_tree(self.tree) |
| 85 | |
| 86 | # Navigate to the correct position in the new tree |
| 87 | node = new_tree |
| 88 | for direction, parent in self.path: |
| 89 | if direction == 'left': |
| 90 | node = node['left'] |
| 91 | else: # direction == 'right' |
| 92 | node = node['right'] |
| 93 | |
| 94 | # Update the value |
| 95 | node['value'] = value |
| 96 | |
| 97 | return Zipper(new_tree, self.path) |
| 98 | |
| 13 | 99 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 100 | """ |
| 101 | Move the focus to the left child of the current node. |
| 102 | |
| 103 | Returns: |
| 104 | A new Zipper focused on the left child, or None if no left child |
| 105 | """ |
| 106 | # Edge Case: Handle None current node |
| 107 | if self._current is None or self._current['left'] is None: |
| 108 | return None |
| 109 | |
| 110 | # Add breadcrumb for current node before moving left |
| 111 | new_path = self.path + [('left', self._current)] |
| 112 | return Zipper(self.tree, new_path) |
| 113 | |
| 16 | 114 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 115 | """ |
| 116 | Set the left child of the focus node. |
| 117 | |
| 118 | Args: |
| 119 | tree: The new left subtree (or None to remove) |
| 120 | |
| 121 | Returns: |
| 122 | A new Zipper with the updated left child |
| 123 | """ |
| 124 | # Create a deep copy of the tree |
| 125 | new_tree = self._deep_copy_tree(self.tree) |
| 126 | |
| 127 | # Navigate to the correct position in the new tree |
| 128 | node = new_tree |
| 129 | for direction, parent in self.path: |
| 130 | if direction == 'left': |
| 131 | node = node['left'] |
| 132 | else: # direction == 'right' |
| 133 | node = node['right'] |
| 134 | |
| 135 | # Update the left child |
| 136 | node['left'] = tree |
| 137 | |
| 138 | return Zipper(new_tree, self.path) |
| 139 | |
| 19 | 140 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 141 | """ |
| 142 | Move the focus to the right child of the current node. |
| 143 | |
| 144 | Returns: |
| 145 | A new Zipper focused on the right child, or None if no right child |
| 146 | """ |
| 147 | # Edge Case: Handle None current node |
| 148 | if self._current is None or self._current['right'] is None: |
| 149 | return None |
| 150 | |
| 151 | # Add breadcrumb for current node before moving right |
| 152 | new_path = self.path + [('right', self._current)] |
| 153 | return Zipper(self.tree, new_path) |
| 154 | |
| 22 | 155 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 156 | """ |
| 157 | Set the right child of the focus node. |
| 158 | |
| 159 | Args: |
| 160 | tree: The new right subtree (or None to remove) |
| 161 | |
| 162 | Returns: |
| 163 | A new Zipper with the updated right child |
| 164 | """ |
| 165 | # Create a deep copy of the tree |
| 166 | new_tree = self._deep_copy_tree(self.tree) |
| 167 | |
| 168 | # Navigate to the correct position in the new tree |
| 169 | node = new_tree |
| 170 | for direction, parent in self.path: |
| 171 | if direction == 'left': |
| 172 | node = node['left'] |
| 173 | else: # direction == 'right' |
| 174 | node = node['right'] |
| 175 | |
| 176 | # Update the right child |
| 177 | node['right'] = tree |
| 178 | |
| 179 | return Zipper(new_tree, self.path) |
| 180 | |
| 25 | 181 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 182 | """ |
| 183 | Move the focus to the parent of the current node. |
| 184 | |
| 185 | Returns: |
| 186 | A new Zipper focused on the parent, or None if at root |
| 187 | """ |
| 188 | # Edge Case: Handle already at root (no parent) |
| 189 | if not self.path: |
| 190 | return None |
| 191 | |
| 192 | # Remove the last breadcrumb to move up |
| 193 | new_path = self.path[:-1] |
| 194 | return Zipper(self.tree, new_path) |
| 195 | |
| 28 | 196 | def to_tree(self) -> dict: |
| 29 | | pass |
| 197 | """ |
| 198 | Get the complete tree from the zipper. |
| 199 | |
| 200 | Returns: |
| 201 | The full tree structure |
| 202 | """ |
| 203 | return self.tree |
| 204 | |
| 205 | def _deep_copy_tree(self, tree): |
| 206 | """ |
| 207 | Create a deep copy of a tree. |
| 208 | |
| 209 | Args: |
| 210 | tree: The tree to copy |
| 211 | |
| 212 | Returns: |
| 213 | A deep copy of the tree |
| 214 | """ |
| 215 | # Edge Case: Handle None tree |
| 216 | if tree is None: |
| 217 | return None |
| 218 | |
| 219 | return { |
| 220 | 'value': tree['value'], |
| 221 | 'left': self._deep_copy_tree(tree['left']), |
| 222 | 'right': self._deep_copy_tree(tree['right']) |
| 223 | } |
| 224 | |
| 225 | # Handled Edge Cases: None tree in from_tree, empty path in _get_current_node, |
| 226 | # None current node in value, None current node in set_value, None current node in left, |
| 227 | # None current node in right, already at root in up, None tree in _deep_copy_tree |