| 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 | navigation and modification operations while preserving the tree structure. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, path): |
| 10 | """ |
| 11 | Initialize a Zipper instance. |
| 12 | |
| 13 | Args: |
| 14 | tree (dict): The current focus node of the tree |
| 15 | path (list): A list of breadcrumb dictionaries representing the path from root to focus |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.path = path |
| 19 | |
| 3 | 20 | @staticmethod |
| 4 | 21 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 22 | """ |
| 23 | Create a zipper from a binary tree. |
| 24 | |
| 25 | Args: |
| 26 | tree (dict): A binary tree represented as nested dictionaries with "value", "left", and "right" keys |
| 27 | |
| 28 | Returns: |
| 29 | Zipper: A new zipper with focus on the root node |
| 30 | """ |
| 31 | # Edge Case: Handle None tree input |
| 32 | if tree is None: |
| 33 | return None |
| 34 | return Zipper(tree, []) |
| 35 | |
| 7 | 36 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 37 | """ |
| 38 | Get the value of the focus node. |
| 39 | |
| 40 | Returns: |
| 41 | int: The value of the focus node |
| 42 | |
| 43 | Raises: |
| 44 | AttributeError: If the focus node is None |
| 45 | """ |
| 46 | # Edge Case: Handle None tree (should not happen in normal usage but added for robustness) |
| 47 | if self.tree is None: |
| 48 | raise AttributeError("Cannot get value of None node") |
| 49 | return self.tree["value"] |
| 50 | |
| 10 | 51 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 52 | """ |
| 53 | Set the value of the focus node. |
| 54 | |
| 55 | Args: |
| 56 | value (int): The new value for the focus node |
| 57 | |
| 58 | Returns: |
| 59 | Zipper: A new zipper with the updated focus node |
| 60 | """ |
| 61 | # Edge Case: Handle None tree |
| 62 | if self.tree is None: |
| 63 | return self |
| 64 | new_tree = {"value": value, "left": self.tree["left"], "right": self.tree["right"]} |
| 65 | return Zipper(new_tree, self.path) |
| 66 | |
| 13 | 67 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 68 | """ |
| 69 | Move the focus to the left child of the current node. |
| 70 | |
| 71 | Returns: |
| 72 | Zipper | None: A new zipper focused on the left child, or None if no left child exists |
| 73 | """ |
| 74 | # Edge Case: Handle None tree |
| 75 | if self.tree is None or self.tree["left"] is None: |
| 76 | return None |
| 77 | |
| 78 | # Create breadcrumb to store current node context when moving down |
| 79 | breadcrumb = { |
| 80 | "parent": self.tree, |
| 81 | "side": "left", |
| 82 | "right": self.tree["right"] |
| 83 | } |
| 84 | |
| 85 | return Zipper(self.tree["left"], self.path + [breadcrumb]) |
| 86 | |
| 16 | 87 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 88 | """ |
| 89 | Set the left child of the focus node. |
| 90 | |
| 91 | Args: |
| 92 | tree (dict | None): The new left subtree or None |
| 93 | |
| 94 | Returns: |
| 95 | Zipper: A new zipper with the updated focus node |
| 96 | """ |
| 97 | # Edge Case: Handle None tree |
| 98 | if self.tree is None: |
| 99 | return self |
| 100 | new_tree = {"value": self.tree["value"], "left": tree, "right": self.tree["right"]} |
| 101 | return Zipper(new_tree, self.path) |
| 102 | |
| 19 | 103 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 104 | """ |
| 105 | Move the focus to the right child of the current node. |
| 106 | |
| 107 | Returns: |
| 108 | Zipper | None: A new zipper focused on the right child, or None if no right child exists |
| 109 | """ |
| 110 | # Edge Case: Handle None tree |
| 111 | if self.tree is None or self.tree["right"] is None: |
| 112 | return None |
| 113 | |
| 114 | # Create breadcrumb to store current node context when moving down |
| 115 | breadcrumb = { |
| 116 | "parent": self.tree, |
| 117 | "side": "right", |
| 118 | "left": self.tree["left"] |
| 119 | } |
| 120 | |
| 121 | return Zipper(self.tree["right"], self.path + [breadcrumb]) |
| 122 | |
| 22 | 123 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 124 | """ |
| 125 | Set the right child of the focus node. |
| 126 | |
| 127 | Args: |
| 128 | tree (dict | None): The new right subtree or None |
| 129 | |
| 130 | Returns: |
| 131 | Zipper: A new zipper with the updated focus node |
| 132 | """ |
| 133 | # Edge Case: Handle None tree |
| 134 | if self.tree is None: |
| 135 | return self |
| 136 | new_tree = {"value": self.tree["value"], "left": self.tree["left"], "right": tree} |
| 137 | return Zipper(new_tree, self.path) |
| 138 | |
| 25 | 139 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 140 | """ |
| 141 | Move the focus to the parent of the current node. |
| 142 | |
| 143 | Returns: |
| 144 | Zipper | None: A new zipper focused on the parent node, or None if already at root |
| 145 | """ |
| 146 | # Edge Case: Handle when already at root (no path) |
| 147 | if not self.path: |
| 148 | return None |
| 149 | |
| 150 | # Get the most recent breadcrumb |
| 151 | breadcrumb = self.path[-1] |
| 152 | |
| 153 | # Reconstruct the parent node with the current tree in the correct position |
| 154 | parent_tree = { |
| 155 | "value": breadcrumb["parent"]["value"], |
| 156 | "left": self.tree if breadcrumb["side"] == "left" else breadcrumb["left"], |
| 157 | "right": self.tree if breadcrumb["side"] == "right" else breadcrumb["right"] |
| 158 | } |
| 159 | |
| 160 | # Return a new zipper focused on the parent with the rest of the path |
| 161 | return Zipper(parent_tree, self.path[:-1]) |
| 162 | |
| 28 | 163 | def to_tree(self) -> dict: |
| 29 | | pass |
| 164 | """ |
| 165 | Get the complete tree from the zipper. |
| 166 | |
| 167 | Returns: |
| 168 | dict: The complete binary tree |
| 169 | """ |
| 170 | # Navigate up to the root to get the complete tree |
| 171 | current = self |
| 172 | while True: |
| 173 | parent = current.up() |
| 174 | if parent is None: |
| 175 | break |
| 176 | current = parent |
| 177 | return current.tree |
| 178 | |
| 179 | # Handled Edge Cases: None tree input, None focus node, moving when no child exists, moving up from root |