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