| 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 tuples representing the path from root to focus |
| 12 | Each tuple contains (parent_node, direction) where direction |
| 13 | is 'left' or 'right' |
| 14 | """ |
| 15 | |
| 16 | def __init__(self, focus: dict, path: list): |
| 17 | """ |
| 18 | Initialize a Zipper with a focus node and path. |
| 19 | |
| 20 | Args: |
| 21 | focus (dict): The node currently in focus |
| 22 | path (list): The path from root to focus |
| 23 | """ |
| 24 | self._focus = focus |
| 25 | self._path = path |
| 26 | |
| 3 | 27 | @staticmethod |
| 4 | 28 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 29 | """ |
| 30 | Create a zipper from a binary tree, with focus on the root node. |
| 31 | |
| 32 | Args: |
| 33 | tree (dict): A binary tree represented as a dict with keys 'value', 'left', 'right' |
| 34 | |
| 35 | Returns: |
| 36 | Zipper: A new zipper with focus on the root of the tree |
| 37 | |
| 38 | # Edge Case: Empty tree (None) |
| 39 | """ |
| 40 | # Handled Edge Cases: Empty tree |
| 41 | if tree is None: |
| 42 | return None |
| 43 | return Zipper(tree, []) |
| 44 | |
| 7 | 45 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 46 | """ |
| 47 | Get the value of the focus node. |
| 48 | |
| 49 | Returns: |
| 50 | int: The value of the focus node |
| 51 | |
| 52 | # Edge Case: Called on None zipper |
| 53 | """ |
| 54 | # Handled Edge Cases: None zipper |
| 55 | if self is None: |
| 56 | return None |
| 57 | return self._focus["value"] |
| 58 | |
| 10 | 59 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 60 | """ |
| 61 | Set the value of the focus node, returning a new zipper. |
| 62 | |
| 63 | Args: |
| 64 | value (int): The new value for the focus node |
| 65 | |
| 66 | Returns: |
| 67 | Zipper: A new zipper with the updated focus node value |
| 68 | |
| 69 | # Edge Case: Called on None zipper |
| 70 | """ |
| 71 | # Handled Edge Cases: None zipper |
| 72 | if self is None: |
| 73 | return None |
| 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 | # Edge Case: Called on None zipper |
| 89 | # Edge Case: No left child |
| 90 | """ |
| 91 | # Handled Edge Cases: None zipper, No left child |
| 92 | if self is None: |
| 93 | return None |
| 94 | if self._focus["left"] is None: |
| 95 | return None |
| 96 | new_path = self._path + [(self._focus, "left")] |
| 97 | return Zipper(self._focus["left"], new_path) |
| 98 | |
| 16 | 99 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 100 | """ |
| 101 | Set the left child of the focus node, returning a new zipper. |
| 102 | |
| 103 | Args: |
| 104 | tree (dict | None): The new left subtree |
| 105 | |
| 106 | Returns: |
| 107 | Zipper: A new zipper with the updated left child |
| 108 | |
| 109 | # Edge Case: Called on None zipper |
| 110 | """ |
| 111 | # Handled Edge Cases: None zipper |
| 112 | if self is None: |
| 113 | return None |
| 114 | new_focus = { |
| 115 | "value": self._focus["value"], |
| 116 | "left": tree, |
| 117 | "right": self._focus["right"] |
| 118 | } |
| 119 | return Zipper(new_focus, self._path) |
| 120 | |
| 19 | 121 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 122 | """ |
| 123 | Move the focus to the right child of the current node. |
| 124 | |
| 125 | Returns: |
| 126 | Zipper | None: A new zipper with focus on the right child, or None if no right child |
| 127 | |
| 128 | # Edge Case: Called on None zipper |
| 129 | # Edge Case: No right child |
| 130 | """ |
| 131 | # Handled Edge Cases: None zipper, No right child |
| 132 | if self is None: |
| 133 | return None |
| 134 | if self._focus["right"] is None: |
| 135 | return None |
| 136 | new_path = self._path + [(self._focus, "right")] |
| 137 | return Zipper(self._focus["right"], new_path) |
| 138 | |
| 22 | 139 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 140 | """ |
| 141 | Set the right child of the focus node, returning a new zipper. |
| 142 | |
| 143 | Args: |
| 144 | tree (dict | None): The new right subtree |
| 145 | |
| 146 | Returns: |
| 147 | Zipper: A new zipper with the updated right child |
| 148 | |
| 149 | # Edge Case: Called on None zipper |
| 150 | """ |
| 151 | # Handled Edge Cases: None zipper |
| 152 | if self is None: |
| 153 | return None |
| 154 | new_focus = { |
| 155 | "value": self._focus["value"], |
| 156 | "left": self._focus["left"], |
| 157 | "right": tree |
| 158 | } |
| 159 | return Zipper(new_focus, self._path) |
| 160 | |
| 25 | 161 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 162 | """ |
| 163 | Move the focus to the parent of the current node. |
| 164 | |
| 165 | Returns: |
| 166 | Zipper | None: A new zipper with focus on the parent, or None if at root |
| 167 | |
| 168 | # Edge Case: Called on None zipper |
| 169 | # Edge Case: Already at root (no parent) |
| 170 | """ |
| 171 | # Handled Edge Cases: None zipper, Already at root |
| 172 | if self is None or not self._path: |
| 173 | return None |
| 174 | |
| 175 | parent, direction = self._path[-1] |
| 176 | new_focus = parent.copy() |
| 177 | |
| 178 | # Update the parent's child reference to match the current focus |
| 179 | if direction == "left": |
| 180 | new_focus["left"] = self._focus |
| 181 | else: # direction == "right" |
| 182 | new_focus["right"] = self._focus |
| 183 | |
| 184 | return Zipper(new_focus, self._path[:-1]) |
| 185 | |
| 28 | 186 | def to_tree(self) -> dict: |
| 29 | | pass |
| 187 | """ |
| 188 | Reconstruct the entire tree from the current zipper state. |
| 189 | |
| 190 | Returns: |
| 191 | dict: The complete binary tree |
| 192 | |
| 193 | # Edge Case: Called on None zipper |
| 194 | """ |
| 195 | # Handled Edge Cases: None zipper |
| 196 | if self is None: |
| 197 | return None |
| 198 | |
| 199 | # Start with the current focus |
| 200 | tree = self._focus |
| 201 | |
| 202 | # Work our way up the path, rebuilding the tree |
| 203 | for node, direction in reversed(self._path): |
| 204 | if direction == "left": |
| 205 | tree = { |
| 206 | "value": node["value"], |
| 207 | "left": tree, |
| 208 | "right": node["right"] |
| 209 | } |
| 210 | else: # direction == "right" |
| 211 | tree = { |
| 212 | "value": node["value"], |
| 213 | "left": node["left"], |
| 214 | "right": tree |
| 215 | } |
| 216 | |
| 217 | return tree |