| 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, allowing for |
| 6 | functional navigation and modification. It stores the path from the root |
| 7 | to the current focus node, enabling movement in all directions. |
| 8 | |
| 9 | Attributes: |
| 10 | _focus (dict): The current node in focus with keys 'value', 'left', 'right' |
| 11 | _path (list): A list of breadcrumbs representing the path from root to focus |
| 12 | """ |
| 13 | |
| 14 | def __init__(self, focus, path): |
| 15 | """ |
| 16 | Initialize a Zipper with a focus node and path. |
| 17 | |
| 18 | Args: |
| 19 | focus (dict): The node currently in focus |
| 20 | path (list): The path from root to focus node |
| 21 | """ |
| 22 | self._focus = focus |
| 23 | self._path = path |
| 24 | |
| 3 | 25 | @staticmethod |
| 4 | 26 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 27 | """ |
| 28 | Create a zipper from a binary tree, with focus on the root node. |
| 29 | |
| 30 | Args: |
| 31 | tree (dict): A binary tree represented as a dict with keys 'value', 'left', 'right' |
| 32 | |
| 33 | Returns: |
| 34 | Zipper: A new zipper with focus on the root of the tree |
| 35 | |
| 36 | Edge Case: Empty tree (None) - Returns a zipper with None focus and empty path |
| 37 | """ |
| 38 | # Edge Case: Empty tree |
| 39 | if tree is None: |
| 40 | return Zipper(None, []) |
| 41 | return Zipper(tree, []) |
| 42 | |
| 7 | 43 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 44 | """ |
| 45 | Get the value of the focus node. |
| 46 | |
| 47 | Returns: |
| 48 | int: The value of the focus node |
| 49 | |
| 50 | Edge Case: Focus is None - Raises AttributeError as operation is invalid |
| 51 | """ |
| 52 | # Edge Case: Focus is None |
| 53 | if self._focus is None: |
| 54 | raise AttributeError("Cannot get value of None focus") |
| 55 | return self._focus["value"] |
| 56 | |
| 10 | 57 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 58 | """ |
| 59 | Set the value of the focus node, returning a new zipper. |
| 60 | |
| 61 | Args: |
| 62 | value (int): The new value for the focus node |
| 63 | |
| 64 | Returns: |
| 65 | Zipper: A new zipper with updated focus node value |
| 66 | |
| 67 | Edge Case: Focus is None - Returns a new zipper with None focus |
| 68 | """ |
| 69 | # Edge Case: Focus is None |
| 70 | if self._focus is None: |
| 71 | return Zipper(None, self._path) |
| 72 | |
| 73 | new_focus = { |
| 74 | "value": value, |
| 75 | "left": self._focus["left"], |
| 76 | "right": self._focus["right"] |
| 77 | } |
| 78 | return Zipper(new_focus, self._path) |
| 79 | |
| 13 | 80 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 81 | """ |
| 82 | Move the focus to the left child of the current focus node. |
| 83 | |
| 84 | Returns: |
| 85 | Zipper | None: A new zipper with focus on the left child, or None if no left child |
| 86 | |
| 87 | Edge Case: Focus is None - Returns None as no navigation is possible |
| 88 | Edge Case: No left child - Returns None as navigation is not possible |
| 89 | """ |
| 90 | # Edge Case: Focus is None |
| 91 | if self._focus is None: |
| 92 | return None |
| 93 | |
| 94 | # Edge Case: No left child |
| 95 | if self._focus["left"] is None: |
| 96 | return None |
| 97 | |
| 98 | # Create a breadcrumb to store the current focus and that we went left |
| 99 | breadcrumb = { |
| 100 | "parent": self._focus, |
| 101 | "which_child": "left", |
| 102 | "sibling": self._focus["right"] # The sibling when we went left |
| 103 | } |
| 104 | |
| 105 | new_path = [breadcrumb] + self._path |
| 106 | return Zipper(self._focus["left"], new_path) |
| 107 | |
| 16 | 108 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 109 | """ |
| 110 | Set the left child of the focus node, returning a new zipper. |
| 111 | |
| 112 | Args: |
| 113 | tree (dict | None): The new left subtree or None |
| 114 | |
| 115 | Returns: |
| 116 | Zipper: A new zipper with updated left child |
| 117 | |
| 118 | Edge Case: Focus is None - Returns a new zipper with None focus |
| 119 | """ |
| 120 | # Edge Case: Focus is None |
| 121 | if self._focus is None: |
| 122 | return Zipper(None, self._path) |
| 123 | |
| 124 | new_focus = { |
| 125 | "value": self._focus["value"], |
| 126 | "left": tree, |
| 127 | "right": self._focus["right"] |
| 128 | } |
| 129 | return Zipper(new_focus, 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 focus node. |
| 134 | |
| 135 | Returns: |
| 136 | Zipper | None: A new zipper with focus on the right child, or None if no right child |
| 137 | |
| 138 | Edge Case: Focus is None - Returns None as no navigation is possible |
| 139 | Edge Case: No right child - Returns None as navigation is not possible |
| 140 | """ |
| 141 | # Edge Case: Focus is None |
| 142 | if self._focus is None: |
| 143 | return None |
| 144 | |
| 145 | # Edge Case: No right child |
| 146 | if self._focus["right"] is None: |
| 147 | return None |
| 148 | |
| 149 | # Create a breadcrumb to store the current focus and that we went right |
| 150 | breadcrumb = { |
| 151 | "parent": self._focus, |
| 152 | "which_child": "right", |
| 153 | "sibling": self._focus["left"] # The sibling when we went right |
| 154 | } |
| 155 | |
| 156 | new_path = [breadcrumb] + self._path |
| 157 | return Zipper(self._focus["right"], new_path) |
| 158 | |
| 22 | 159 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 160 | """ |
| 161 | Set the right child of the focus node, returning a new zipper. |
| 162 | |
| 163 | Args: |
| 164 | tree (dict | None): The new right subtree or None |
| 165 | |
| 166 | Returns: |
| 167 | Zipper: A new zipper with updated right child |
| 168 | |
| 169 | Edge Case: Focus is None - Returns a new zipper with None focus |
| 170 | """ |
| 171 | # Edge Case: Focus is None |
| 172 | if self._focus is None: |
| 173 | return Zipper(None, self._path) |
| 174 | |
| 175 | new_focus = { |
| 176 | "value": self._focus["value"], |
| 177 | "left": self._focus["left"], |
| 178 | "right": tree |
| 179 | } |
| 180 | return Zipper(new_focus, self._path) |
| 181 | |
| 25 | 182 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 183 | """ |
| 184 | Move the focus to the parent of the current focus node. |
| 185 | |
| 186 | Returns: |
| 187 | Zipper | None: A new zipper with focus on the parent, or None if at root |
| 188 | |
| 189 | Edge Case: At root (empty path) - Returns None as no parent exists |
| 190 | Edge Case: Focus is None - Returns None as navigation is not possible |
| 191 | """ |
| 192 | # Edge Case: Focus is None |
| 193 | if self._focus is None: |
| 194 | return None |
| 195 | |
| 196 | # Edge Case: At root (no path) |
| 197 | if not self._path: |
| 198 | return None |
| 199 | |
| 200 | # Get the top breadcrumb |
| 201 | breadcrumb = self._path[0] |
| 202 | parent = breadcrumb["parent"] |
| 203 | which_child = breadcrumb["which_child"] |
| 204 | sibling = breadcrumb["sibling"] |
| 205 | |
| 206 | # Reconstruct the parent with the current focus as the appropriate child |
| 207 | new_parent = { |
| 208 | "value": parent["value"], |
| 209 | "left": self._focus if which_child == "left" else sibling, |
| 210 | "right": self._focus if which_child == "right" else sibling |
| 211 | } |
| 212 | |
| 213 | return Zipper(new_parent, self._path[1:]) |
| 214 | |
| 28 | 215 | def to_tree(self) -> dict: |
| 29 | | pass |
| 216 | """ |
| 217 | Get the complete binary tree from the zipper. |
| 218 | |
| 219 | Returns: |
| 220 | dict: The complete binary tree |
| 221 | |
| 222 | Edge Case: Focus is None - Reconstructs tree from path if possible, otherwise returns None |
| 223 | """ |
| 224 | # Start with the current focus |
| 225 | current = self._focus |
| 226 | |
| 227 | # Edge Case: Focus is None but we have a path |
| 228 | # This could happen if we deleted the root |
| 229 | if current is None and not self._path: |
| 230 | return None |
| 231 | |
| 232 | # Traverse up the path to reconstruct the tree |
| 233 | for breadcrumb in self._path: |
| 234 | parent = breadcrumb["parent"] |
| 235 | which_child = breadcrumb["which_child"] |
| 236 | sibling = breadcrumb["sibling"] |
| 237 | |
| 238 | # Reconstruct the parent with current as the appropriate child |
| 239 | if which_child == "left": |
| 240 | current = { |
| 241 | "value": parent["value"], |
| 242 | "left": current, |
| 243 | "right": sibling |
| 244 | } |
| 245 | else: # which_child == "right" |
| 246 | current = { |
| 247 | "value": parent["value"], |
| 248 | "left": sibling, |
| 249 | "right": current |
| 250 | } |
| 251 | |
| 252 | return current |
| 253 | |
| 254 | # Handled Edge Cases: Empty tree, focus is None, no left child, no right child, at root |