| 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 contains a data structure and a pointer (focus) into that data structure. |
| 6 | It supports functional navigation and manipulation operations. |
| 7 | |
| 8 | Attributes: |
| 9 | _focus (dict): The current node in focus with keys 'value', 'left', 'right' |
| 10 | _path (list): A list of tuples representing the path from root to focus |
| 11 | Each tuple contains (parent_node, is_left_child) |
| 12 | """ |
| 13 | |
| 14 | def __init__(self, focus: dict, path: list): |
| 15 | """ |
| 16 | Initialize a Zipper. |
| 17 | |
| 18 | Args: |
| 19 | focus (dict): The node currently in focus |
| 20 | path (list): The path from root to focus |
| 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. |
| 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 node |
| 35 | |
| 36 | # Handled Edge Cases: None (tree is assumed to be valid per problem constraints) |
| 37 | """ |
| 38 | # Edge Case: Handle None tree by creating an empty focus |
| 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 | # Handled Edge Cases: Focus node is None |
| 51 | """ |
| 52 | # Edge Case: If focus is None, return None or raise an exception |
| 53 | # Based on problem context, we assume valid operations, but we should handle None |
| 54 | if self._focus is None: |
| 55 | return None |
| 56 | return self._focus["value"] |
| 57 | |
| 10 | 58 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 59 | """ |
| 60 | Set the value of the focus node. |
| 61 | |
| 62 | Args: |
| 63 | value (int): The new value for the focus node |
| 64 | |
| 65 | Returns: |
| 66 | Zipper: A new zipper with updated focus node value |
| 67 | |
| 68 | # Handled Edge Cases: Focus node is None |
| 69 | """ |
| 70 | # Edge Case: If focus is None, we can't set a value |
| 71 | if self._focus is None: |
| 72 | return self |
| 73 | |
| 74 | new_focus = { |
| 75 | "value": value, |
| 76 | "left": self._focus["left"], |
| 77 | "right": self._focus["right"] |
| 78 | } |
| 79 | return Zipper(new_focus, 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 with focus on the left child, or None if no left child |
| 87 | |
| 88 | # Handled Edge Cases: Focus node is None, No left child exists |
| 89 | """ |
| 90 | # Edge Case: If focus is None, we can't move left |
| 91 | if self._focus is None: |
| 92 | return None |
| 93 | |
| 94 | # Edge Case: If there's no left child, return None |
| 95 | if self._focus["left"] is None: |
| 96 | return None |
| 97 | |
| 98 | # Create a new path entry: (current_focus, True) where True indicates we went left |
| 99 | new_path = [(self._focus, True)] + self._path |
| 100 | return Zipper(self._focus["left"], new_path) |
| 101 | |
| 16 | 102 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 103 | """ |
| 104 | Set the left child of the focus node. |
| 105 | |
| 106 | Args: |
| 107 | tree (dict | None): The new left subtree |
| 108 | |
| 109 | Returns: |
| 110 | Zipper: A new zipper with updated left child |
| 111 | |
| 112 | # Handled Edge Cases: Focus node is None |
| 113 | """ |
| 114 | # Edge Case: If focus is None, we can't set a left child |
| 115 | if self._focus is None: |
| 116 | return self |
| 117 | |
| 118 | new_focus = { |
| 119 | "value": self._focus["value"], |
| 120 | "left": tree, |
| 121 | "right": self._focus["right"] |
| 122 | } |
| 123 | return Zipper(new_focus, self._path) |
| 124 | |
| 19 | 125 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 126 | """ |
| 127 | Move the focus to the right child of the current node. |
| 128 | |
| 129 | Returns: |
| 130 | Zipper | None: A new zipper with focus on the right child, or None if no right child |
| 131 | |
| 132 | # Handled Edge Cases: Focus node is None, No right child exists |
| 133 | """ |
| 134 | # Edge Case: If focus is None, we can't move right |
| 135 | if self._focus is None: |
| 136 | return None |
| 137 | |
| 138 | # Edge Case: If there's no right child, return None |
| 139 | if self._focus["right"] is None: |
| 140 | return None |
| 141 | |
| 142 | # Create a new path entry: (current_focus, False) where False indicates we went right |
| 143 | new_path = [(self._focus, False)] + self._path |
| 144 | return Zipper(self._focus["right"], 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. |
| 149 | |
| 150 | Args: |
| 151 | tree (dict | None): The new right subtree |
| 152 | |
| 153 | Returns: |
| 154 | Zipper: A new zipper with updated right child |
| 155 | |
| 156 | # Handled Edge Cases: Focus node is None |
| 157 | """ |
| 158 | # Edge Case: If focus is None, we can't set a right child |
| 159 | if self._focus is None: |
| 160 | return self |
| 161 | |
| 162 | new_focus = { |
| 163 | "value": self._focus["value"], |
| 164 | "left": self._focus["left"], |
| 165 | "right": tree |
| 166 | } |
| 167 | return Zipper(new_focus, self._path) |
| 168 | |
| 25 | 169 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 170 | """ |
| 171 | Move the focus to the parent node. |
| 172 | |
| 173 | Returns: |
| 174 | Zipper | None: A new zipper with focus on the parent, or None if at root |
| 175 | |
| 176 | # Handled Edge Cases: Already at root (no parent), Focus node is None |
| 177 | """ |
| 178 | # Edge Case: If focus is None, we can't move up |
| 179 | if self._focus is None: |
| 180 | return None |
| 181 | |
| 182 | # Edge Case: If path is empty, we're at the root and can't go up |
| 183 | if not self._path: |
| 184 | return None |
| 185 | |
| 186 | # Get the parent node and whether we were in the left subtree |
| 187 | parent, is_left = self._path[0] |
| 188 | |
| 189 | # Reconstruct the parent with the current focus as the appropriate child |
| 190 | if is_left: |
| 191 | new_parent = { |
| 192 | "value": parent["value"], |
| 193 | "left": self._focus, |
| 194 | "right": parent["right"] |
| 195 | } |
| 196 | else: |
| 197 | new_parent = { |
| 198 | "value": parent["value"], |
| 199 | "left": parent["left"], |
| 200 | "right": self._focus |
| 201 | } |
| 202 | |
| 203 | # Return a new zipper with the parent as focus and the rest of the path |
| 204 | return Zipper(new_parent, self._path[1:]) |
| 205 | |
| 28 | 206 | def to_tree(self) -> dict: |
| 29 | | pass |
| 207 | """ |
| 208 | Get the complete binary tree from the zipper. |
| 209 | |
| 210 | Returns: |
| 211 | dict: The complete binary tree |
| 212 | |
| 213 | # Handled Edge Cases: Focus node is None |
| 214 | """ |
| 215 | # Edge Case: If focus is None, return None |
| 216 | if self._focus is None: |
| 217 | return None |
| 218 | |
| 219 | # Start with the current focus |
| 220 | tree = self._focus |
| 221 | |
| 222 | # Reconstruct the tree by moving up the path |
| 223 | for parent, is_left in self._path: |
| 224 | if is_left: |
| 225 | tree = { |
| 226 | "value": parent["value"], |
| 227 | "left": tree, |
| 228 | "right": parent["right"] |
| 229 | } |
| 230 | else: |
| 231 | tree = { |
| 232 | "value": parent["value"], |
| 233 | "left": parent["left"], |
| 234 | "right": tree |
| 235 | } |
| 236 | |
| 237 | return tree |