| 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 and allows |
| 6 | traversal and modification operations. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, path=None): |
| 10 | """ |
| 11 | Initialize a Zipper. |
| 12 | |
| 13 | Args: |
| 14 | tree (dict): The tree structure |
| 15 | path (list): Path from root to current focus node |
| 16 | """ |
| 17 | # Edge Case: Handle None tree by initializing with empty structure |
| 18 | if tree is None: |
| 19 | tree = {"value": 0, "left": None, "right": None} |
| 20 | self.tree = tree |
| 21 | # Edge Case: Initialize path as empty list if not provided |
| 22 | self.path = path or [] |
| 23 | |
| 3 | 24 | @staticmethod |
| 4 | 25 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 26 | """ |
| 27 | Create a zipper from a tree, with focus on the root node. |
| 28 | |
| 29 | Args: |
| 30 | tree (dict): The tree to create a zipper for |
| 31 | |
| 32 | Returns: |
| 33 | Zipper: A new zipper focused on the root of the tree |
| 34 | """ |
| 35 | # Edge Case: Handle None tree input |
| 36 | if tree is None: |
| 37 | return Zipper(None) |
| 38 | return Zipper(tree) |
| 39 | |
| 40 | def _get_focus_node(self): |
| 41 | """ |
| 42 | Get the current focus node based on the path. |
| 43 | |
| 44 | Returns: |
| 45 | dict: The focus node |
| 46 | """ |
| 47 | node = self.tree |
| 48 | for direction, parent in self.path: |
| 49 | node = node[direction] |
| 50 | return node |
| 51 | |
| 7 | 52 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 53 | """ |
| 54 | Get the value of the focus node. |
| 55 | |
| 56 | Returns: |
| 57 | int: The value of the focus node |
| 58 | """ |
| 59 | return self._get_focus_node()["value"] |
| 60 | |
| 10 | 61 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 62 | """ |
| 63 | Set the value of the focus node, returning a new zipper. |
| 64 | |
| 65 | Args: |
| 66 | value (int): The new value |
| 67 | |
| 68 | Returns: |
| 69 | Zipper: A new zipper with updated value |
| 70 | """ |
| 71 | # Edge Case: Handle None value by using 0 as default |
| 72 | if value is None: |
| 73 | value = 0 |
| 74 | |
| 75 | new_tree = self._copy_tree() |
| 76 | node = new_tree |
| 77 | for direction, parent in self.path: |
| 78 | node = node[direction] |
| 79 | node["value"] = value |
| 80 | return Zipper(new_tree, list(self.path)) |
| 81 | |
| 13 | 82 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 83 | """ |
| 84 | Move the focus to the left child, returning a new zipper. |
| 85 | |
| 86 | Returns: |
| 87 | Zipper | None: A new zipper focused on the left child, or None if no left child |
| 88 | """ |
| 89 | focus = self._get_focus_node() |
| 90 | # Edge Case: Return None if no left child exists |
| 91 | if focus["left"] is None: |
| 92 | return None |
| 93 | new_path = list(self.path) |
| 94 | new_path.append(("left", focus)) |
| 95 | return Zipper(self.tree, new_path) |
| 96 | |
| 16 | 97 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 98 | """ |
| 99 | Set the left child of the focus node, returning a new zipper. |
| 100 | |
| 101 | Args: |
| 102 | tree (dict | None): The new left subtree |
| 103 | |
| 104 | Returns: |
| 105 | Zipper: A new zipper with updated left child |
| 106 | """ |
| 107 | new_tree = self._copy_tree() |
| 108 | node = new_tree |
| 109 | for direction, parent in self.path: |
| 110 | node = node[direction] |
| 111 | node["left"] = tree |
| 112 | return Zipper(new_tree, list(self.path)) |
| 113 | |
| 19 | 114 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 115 | """ |
| 116 | Move the focus to the right child, returning a new zipper. |
| 117 | |
| 118 | Returns: |
| 119 | Zipper | None: A new zipper focused on the right child, or None if no right child |
| 120 | """ |
| 121 | focus = self._get_focus_node() |
| 122 | # Edge Case: Return None if no right child exists |
| 123 | if focus["right"] is None: |
| 124 | return None |
| 125 | new_path = list(self.path) |
| 126 | new_path.append(("right", focus)) |
| 127 | return Zipper(self.tree, new_path) |
| 128 | |
| 22 | 129 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 130 | """ |
| 131 | Set the right child of the focus node, returning a new zipper. |
| 132 | |
| 133 | Args: |
| 134 | tree (dict | None): The new right subtree |
| 135 | |
| 136 | Returns: |
| 137 | Zipper: A new zipper with updated right child |
| 138 | """ |
| 139 | new_tree = self._copy_tree() |
| 140 | node = new_tree |
| 141 | for direction, parent in self.path: |
| 142 | node = node[direction] |
| 143 | node["right"] = tree |
| 144 | return Zipper(new_tree, list(self.path)) |
| 145 | |
| 25 | 146 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 147 | """ |
| 148 | Move the focus to the parent, returning a new zipper. |
| 149 | |
| 150 | Returns: |
| 151 | Zipper | None: A new zipper focused on the parent, or None if at root |
| 152 | """ |
| 153 | # Edge Case: Return None if already at root (no parent) |
| 154 | if not self.path: |
| 155 | return None |
| 156 | new_path = list(self.path) |
| 157 | new_path.pop() |
| 158 | return Zipper(self.tree, new_path) |
| 159 | |
| 28 | 160 | def to_tree(self) -> dict: |
| 29 | | pass |
| 161 | """ |
| 162 | Get the tree representation from the zipper. |
| 163 | |
| 164 | Returns: |
| 165 | dict: The tree structure |
| 166 | """ |
| 167 | return self.tree |
| 168 | |
| 169 | def _copy_tree(self): |
| 170 | """ |
| 171 | Create a deep copy of the tree. |
| 172 | |
| 173 | Returns: |
| 174 | dict: A deep copy of the tree |
| 175 | """ |
| 176 | def _deep_copy(node): |
| 177 | if node is None: |
| 178 | return None |
| 179 | return { |
| 180 | "value": node["value"], |
| 181 | "left": _deep_copy(node["left"]), |
| 182 | "right": _deep_copy(node["right"]) |
| 183 | } |
| 184 | return _deep_copy(self.tree) |
| 185 | |
| 186 | # Handled Edge Cases: None tree input, None value input, no left child, no right child, already at root |