| 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 root tree structure |
| 15 | path: A list of (parent_tree, is_left_child) tuples representing the path from root to focus |
| 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 parent, is_left in self.path: |
| 23 | if is_left: |
| 24 | self.focus = parent['left'] |
| 25 | else: |
| 26 | self.focus = parent['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: A binary tree represented as a dict with keys "value", "left", and "right" |
| 35 | |
| 36 | Returns: |
| 37 | A new Zipper instance focused on the root of the tree |
| 38 | """ |
| 39 | # Edge Case: Handle None tree input |
| 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 | The value of the focus node |
| 50 | """ |
| 51 | # Edge Case: Handle None focus |
| 52 | if self.focus is None: |
| 53 | return None |
| 54 | return self.focus['value'] |
| 55 | |
| 10 | 56 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 57 | """ |
| 58 | Set the value of the focus node, returning a new zipper. |
| 59 | |
| 60 | Args: |
| 61 | value: The new value for the focus node |
| 62 | |
| 63 | Returns: |
| 64 | A new Zipper with the updated value |
| 65 | """ |
| 66 | # Edge Case: Handle None focus |
| 67 | if self.focus is None: |
| 68 | return self |
| 69 | |
| 70 | # Create a new tree structure with the updated value |
| 71 | new_tree = self._copy_tree(self.tree) |
| 72 | |
| 73 | # Navigate to the focus position in the new tree |
| 74 | current = new_tree |
| 75 | for parent, is_left in self.path: |
| 76 | if is_left: |
| 77 | current = current['left'] |
| 78 | else: |
| 79 | current = current['right'] |
| 80 | |
| 81 | # Update the value |
| 82 | current['value'] = value |
| 83 | |
| 84 | return Zipper(new_tree, self.path) |
| 85 | |
| 13 | 86 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 87 | """ |
| 88 | Move the focus to the left child of the current node. |
| 89 | |
| 90 | Returns: |
| 91 | A new Zipper focused on the left child, or None if no left child exists |
| 92 | """ |
| 93 | # Edge Case: Handle None focus |
| 94 | if self.focus is None or self.focus['left'] is None: |
| 95 | return None |
| 96 | |
| 97 | # Create a new path with the current focus added |
| 98 | new_path = self.path + [(self.focus, True)] |
| 99 | return Zipper(self.tree, new_path) |
| 100 | |
| 16 | 101 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 102 | """ |
| 103 | Set the left child of the focus node, returning a new zipper. |
| 104 | |
| 105 | Args: |
| 106 | tree: The new left subtree (or None to remove the left child) |
| 107 | |
| 108 | Returns: |
| 109 | A new Zipper with the updated left child |
| 110 | """ |
| 111 | # Edge Case: Handle None focus |
| 112 | if self.focus is None: |
| 113 | return self |
| 114 | |
| 115 | # Create a new tree structure with the updated left child |
| 116 | new_tree = self._copy_tree(self.tree) |
| 117 | |
| 118 | # Navigate to the focus position in the new tree |
| 119 | current = new_tree |
| 120 | for parent, is_left in self.path: |
| 121 | if is_left: |
| 122 | current = current['left'] |
| 123 | else: |
| 124 | current = current['right'] |
| 125 | |
| 126 | # Update the left child |
| 127 | current['left'] = tree |
| 128 | |
| 129 | return Zipper(new_tree, self.path) |
| 130 | |
| 19 | 131 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 132 | """ |
| 133 | Move the focus to the right child of the current node. |
| 134 | |
| 135 | Returns: |
| 136 | A new Zipper focused on the right child, or None if no right child exists |
| 137 | """ |
| 138 | # Edge Case: Handle None focus |
| 139 | if self.focus is None or self.focus['right'] is None: |
| 140 | return None |
| 141 | |
| 142 | # Create a new path with the current focus added |
| 143 | new_path = self.path + [(self.focus, False)] |
| 144 | return Zipper(self.tree, new_path) |
| 145 | |
| 22 | 146 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 147 | """ |
| 148 | Set the right child of the focus node, returning a new zipper. |
| 149 | |
| 150 | Args: |
| 151 | tree: The new right subtree (or None to remove the right child) |
| 152 | |
| 153 | Returns: |
| 154 | A new Zipper with the updated right child |
| 155 | """ |
| 156 | # Edge Case: Handle None focus |
| 157 | if self.focus is None: |
| 158 | return self |
| 159 | |
| 160 | # Create a new tree structure with the updated right child |
| 161 | new_tree = self._copy_tree(self.tree) |
| 162 | |
| 163 | # Navigate to the focus position in the new tree |
| 164 | current = new_tree |
| 165 | for parent, is_left in self.path: |
| 166 | if is_left: |
| 167 | current = current['left'] |
| 168 | else: |
| 169 | current = current['right'] |
| 170 | |
| 171 | # Update the right child |
| 172 | current['right'] = tree |
| 173 | |
| 174 | return Zipper(new_tree, self.path) |
| 175 | |
| 25 | 176 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 177 | """ |
| 178 | Move the focus to the parent of the current node. |
| 179 | |
| 180 | Returns: |
| 181 | A new Zipper focused on the parent, or None if already at the root |
| 182 | """ |
| 183 | # Edge Case: Handle None path (already at root) |
| 184 | if not self.path: |
| 185 | return None |
| 186 | |
| 187 | # Create a new path without the last element |
| 188 | new_path = self.path[:-1] |
| 189 | return Zipper(self.tree, new_path) |
| 190 | |
| 28 | 191 | def to_tree(self) -> dict: |
| 29 | | pass |
| 192 | """ |
| 193 | Get the complete tree from the zipper. |
| 194 | |
| 195 | Returns: |
| 196 | The complete binary tree |
| 197 | """ |
| 198 | return self.tree |
| 199 | |
| 200 | def _copy_tree(self, tree): |
| 201 | """ |
| 202 | Create a deep copy of a binary tree. |
| 203 | |
| 204 | Args: |
| 205 | tree: The tree to copy |
| 206 | |
| 207 | Returns: |
| 208 | A deep copy of the tree |
| 209 | """ |
| 210 | # Edge Case: Handle None tree |
| 211 | if tree is None: |
| 212 | return None |
| 213 | |
| 214 | return { |
| 215 | 'value': tree['value'], |
| 216 | 'left': self._copy_tree(tree['left']), |
| 217 | 'right': self._copy_tree(tree['right']) |
| 218 | } |
| 219 | |
| 220 | # Handled Edge Cases: None tree input, None focus, None path (root), None left/right children |