| 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 structure. |
| 6 | It supports moving through the tree and modifying it in a functional way. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, breadcrumbs=None): |
| 10 | """ |
| 11 | Initialize a Zipper. |
| 12 | |
| 13 | Args: |
| 14 | tree: The current subtree (focus) as a dict with keys 'value', 'left', 'right' |
| 15 | breadcrumbs: A list of tuples tracking the path from root to current node |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.breadcrumbs = breadcrumbs or [] |
| 19 | |
| 3 | 20 | @staticmethod |
| 4 | 21 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 22 | """ |
| 23 | Create a zipper from a binary tree. |
| 24 | |
| 25 | Args: |
| 26 | tree: A binary tree represented as a dict with keys 'value', 'left', 'right' |
| 27 | |
| 6 | 28 | |
| 29 | Returns: |
| 30 | A new Zipper instance focused on the root of the tree |
| 31 | |
| 32 | |
| 33 | Edge Case: Empty tree (None) is handled by creating an empty zipper |
| 34 | """ |
| 35 | # Edge Case: Handle None tree |
| 36 | if tree is None: |
| 37 | return Zipper(None, []) |
| 38 | return Zipper(tree, []) |
| 39 | |
| 7 | 40 | def value(self) -> int: |
| 8 | | pass |
| 41 | """ |
| 42 | Get the value of the focus node. |
| 43 | |
| 44 | |
| 45 | Returns: |
| 46 | The value of the current node |
| 47 | |
| 9 | 48 | |
| 49 | Edge Case: If the current node is None, this would raise an error in a real implementation, |
| 50 | but according to the problem definition, we assume we're always at a valid node when calling this method |
| 51 | """ |
| 52 | return self.tree["value"] |
| 53 | |
| 10 | 54 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 55 | """ |
| 56 | Set the value of the focus node, returning a new zipper. |
| 57 | |
| 58 | Args: |
| 59 | value: The new value for the focus node |
| 60 | |
| 61 | |
| 62 | Returns: |
| 63 | A new Zipper instance with the updated value |
| 64 | |
| 12 | 65 | |
| 66 | Edge Case: If the current node is None, creates a new node with the given value |
| 67 | """ |
| 68 | # Edge Case: Handle case where current tree is None |
| 69 | if self.tree is None: |
| 70 | new_tree = {"value": value, "left": None, "right": None} |
| 71 | else: |
| 72 | new_tree = {"value": value, "left": self.tree["left"], "right": self.tree["right"]} |
| 73 | return Zipper(new_tree, self.breadcrumbs) |
| 74 | |
| 13 | 75 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 76 | """ |
| 77 | Move the focus to the left child of the current node. |
| 78 | |
| 15 | 79 | |
| 80 | Returns: |
| 81 | A new Zipper focused on the left child, or None if there is no left child |
| 82 | |
| 83 | |
| 84 | Edge Case: If the current node is None or has no left child, returns None |
| 85 | """ |
| 86 | # Edge Case: Handle None tree or missing left child |
| 87 | if self.tree is None or self.tree["left"] is None: |
| 88 | return None |
| 89 | |
| 90 | # Create breadcrumb to remember how to get back to parent |
| 91 | breadcrumb = { |
| 92 | "parent": { |
| 93 | "value": self.tree["value"], |
| 94 | "right": self.tree["right"] |
| 95 | }, |
| 96 | "is_left": True |
| 97 | } |
| 98 | |
| 99 | new_breadcrumbs = [breadcrumb] + self.breadcrumbs |
| 100 | return Zipper(self.tree["left"], new_breadcrumbs) |
| 101 | |
| 16 | 102 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 103 | """ |
| 104 | Set the left child of the focus node, returning a new zipper. |
| 105 | |
| 106 | Args: |
| 107 | tree: The new left subtree (or None to remove the left child) |
| 108 | |
| 109 | |
| 110 | Returns: |
| 111 | A new Zipper instance with the updated left child |
| 112 | |
| 18 | 113 | |
| 114 | Edge Case: If the current node is None, creates a new node with the given left subtree |
| 115 | """ |
| 116 | # Edge Case: Handle case where current tree is None |
| 117 | if self.tree is None: |
| 118 | new_tree = {"value": 0, "left": tree, "right": None} # Default value of 0 |
| 119 | else: |
| 120 | new_tree = {"value": self.tree["value"], "left": tree, "right": self.tree["right"]} |
| 121 | return Zipper(new_tree, self.breadcrumbs) |
| 122 | |
| 19 | 123 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 124 | """ |
| 125 | Move the focus to the right child of the current node. |
| 126 | |
| 21 | 127 | |
| 128 | Returns: |
| 129 | A new Zipper focused on the right child, or None if there is no right child |
| 130 | |
| 131 | |
| 132 | Edge Case: If the current node is None or has no right child, returns None |
| 133 | """ |
| 134 | # Edge Case: Handle None tree or missing right child |
| 135 | if self.tree is None or self.tree["right"] is None: |
| 136 | return None |
| 137 | |
| 138 | # Create breadcrumb to remember how to get back to parent |
| 139 | breadcrumb = { |
| 140 | "parent": { |
| 141 | "value": self.tree["value"], |
| 142 | "left": self.tree["left"] |
| 143 | }, |
| 144 | "is_left": False |
| 145 | } |
| 146 | |
| 147 | new_breadcrumbs = [breadcrumb] + self.breadcrumbs |
| 148 | return Zipper(self.tree["right"], new_breadcrumbs) |
| 149 | |
| 22 | 150 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 151 | """ |
| 152 | Set the right child of the focus node, returning a new zipper. |
| 153 | |
| 154 | Args: |
| 155 | tree: The new right subtree (or None to remove the right child) |
| 156 | |
| 157 | |
| 158 | Returns: |
| 159 | A new Zipper instance with the updated right child |
| 160 | |
| 24 | 161 | |
| 162 | Edge Case: If the current node is None, creates a new node with the given right subtree |
| 163 | """ |
| 164 | # Edge Case: Handle case where current tree is None |
| 165 | if self.tree is None: |
| 166 | new_tree = {"value": 0, "left": None, "right": tree} # Default value of 0 |
| 167 | else: |
| 168 | new_tree = {"value": self.tree["value"], "left": self.tree["left"], "right": tree} |
| 169 | return Zipper(new_tree, self.breadcrumbs) |
| 170 | |
| 25 | 171 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 172 | """ |
| 173 | Move the focus to the parent of the current node. |
| 174 | |
| 175 | |
| 176 | Returns: |
| 177 | A new Zipper focused on the parent, or None if there is no parent (at root) |
| 178 | |
| 27 | 179 | |
| 180 | Edge Case: If there are no breadcrumbs (at root), returns None |
| 181 | """ |
| 182 | # Edge Case: Handle case where we're at the root (no breadcrumbs) |
| 183 | if not self.breadcrumbs: |
| 184 | return None |
| 185 | |
| 186 | breadcrumb = self.breadcrumbs[0] |
| 187 | parent = breadcrumb["parent"] |
| 188 | rest_breadcrumbs = self.breadcrumbs[1:] |
| 189 | |
| 190 | # Reconstruct the parent node with the current tree as the appropriate child |
| 191 | if breadcrumb["is_left"]: |
| 192 | reconstructed_tree = { |
| 193 | "value": parent["value"], |
| 194 | "left": self.tree, |
| 195 | "right": parent["right"] |
| 196 | } |
| 197 | else: |
| 198 | reconstructed_tree = { |
| 199 | "value": parent["value"], |
| 200 | "left": parent["left"], |
| 201 | "right": self.tree |
| 202 | } |
| 203 | |
| 204 | return Zipper(reconstructed_tree, rest_breadcrumbs) |
| 205 | |
| 28 | 206 | def to_tree(self) -> dict: |
| 29 | | pass |
| 207 | """ |
| 208 | Get the entire binary tree from the zipper. |
| 209 | |
| 210 | |
| 211 | Returns: |
| 212 | The complete binary tree as a dict |
| 213 | |
| 214 | |
| 215 | Edge Case: If the zipper is at the root, returns the current tree directly |
| 216 | Edge Case: If the zipper is not at the root, navigates up to reconstruct the full tree |
| 217 | """ |
| 218 | # Start with the current tree |
| 219 | current_zipper = Zipper(self.tree, self.breadcrumbs) |
| 220 | |
| 221 | # Navigate up to the root |
| 222 | while True: |
| 223 | parent_zipper = current_zipper.up() |
| 224 | if parent_zipper is None: |
| 225 | break |
| 226 | current_zipper = parent_zipper |
| 227 | |
| 228 | return current_zipper.tree |
| 229 | |
| 230 | # Handled Edge Cases: Empty tree, None tree, missing children, root node navigation, value setting on None node, child setting on None node |