| 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 a binary tree that allows navigation and manipulation. |
| 4 | |
| 5 | The zipper maintains a focus on a node in the tree and allows movement |
| 6 | up, left, and right, as well as modification of the tree structure. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, breadcrumbs=None): |
| 10 | """ |
| 11 | Initialize a Zipper. |
| 12 | |
| 13 | Args: |
| 14 | tree: The current subtree (focus) |
| 15 | breadcrumbs: Path back to the root, containing parent info |
| 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 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 focus node |
| 47 | |
| 9 | 48 | |
| 49 | Edge Case: If the tree is None, this would raise an error, but we assume valid state |
| 50 | """ |
| 51 | # Edge Case: If tree is None, this operation is invalid |
| 52 | if self.tree is None: |
| 53 | raise ValueError("Cannot get value of None tree") |
| 54 | return self.tree["value"] |
| 55 | |
| 10 | 56 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 57 | """ |
| 58 | Set the value of the focus node. |
| 59 | |
| 60 | Args: |
| 61 | value: The new value for the focus node |
| 62 | |
| 63 | |
| 64 | Returns: |
| 65 | A new Zipper with the updated value |
| 66 | |
| 12 | 67 | |
| 68 | Edge Case: If the tree is None, we create a new node |
| 69 | """ |
| 70 | # Edge Case: If tree is None, create a new node |
| 71 | if self.tree is None: |
| 72 | new_tree = {"value": value, "left": None, "right": None} |
| 73 | else: |
| 74 | new_tree = {"value": value, "left": self.tree["left"], "right": self.tree["right"]} |
| 75 | return Zipper(new_tree, self.breadcrumbs) |
| 76 | |
| 13 | 77 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 78 | """ |
| 79 | Move the focus to the left child. |
| 80 | |
| 15 | 81 | |
| 82 | Returns: |
| 83 | A new Zipper focused on the left child, or None if no left child |
| 84 | |
| 85 | |
| 86 | Edge Case: If the tree is None or has no left child, return None |
| 87 | """ |
| 88 | # Edge Case: If tree is None or has no left child |
| 89 | if self.tree is None or self.tree["left"] is None: |
| 90 | return None |
| 91 | |
| 92 | # Create breadcrumb to remember current node when going back up |
| 93 | breadcrumb = { |
| 94 | "parent": self.tree, |
| 95 | "side": "left", |
| 96 | "right": self.tree["right"] |
| 97 | } |
| 98 | |
| 99 | return Zipper(self.tree["left"], self.breadcrumbs + [breadcrumb]) |
| 100 | |
| 16 | 101 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 102 | """ |
| 103 | Set the left child of the focus node. |
| 104 | |
| 105 | Args: |
| 106 | tree: The new left subtree (or None) |
| 107 | |
| 108 | |
| 109 | Returns: |
| 110 | A new Zipper with the updated left child |
| 111 | |
| 18 | 112 | |
| 113 | Edge Case: If the tree is None, we create a new node |
| 114 | """ |
| 115 | # Edge Case: If tree is None, create a new node |
| 116 | if self.tree is None: |
| 117 | new_tree = {"value": 0, "left": tree, "right": None} # Default value 0 |
| 118 | else: |
| 119 | new_tree = {"value": self.tree["value"], "left": tree, "right": self.tree["right"]} |
| 120 | return Zipper(new_tree, self.breadcrumbs) |
| 121 | |
| 19 | 122 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 123 | """ |
| 124 | Move the focus to the right child. |
| 125 | |
| 126 | |
| 127 | Returns: |
| 128 | A new Zipper focused on the right child, or None if no right child |
| 129 | |
| 21 | 130 | |
| 131 | Edge Case: If the tree is None or has no right child, return None |
| 132 | """ |
| 133 | # Edge Case: If tree is None or has no right child |
| 134 | if self.tree is None or self.tree["right"] is None: |
| 135 | return None |
| 136 | |
| 137 | # Create breadcrumb to remember current node when going back up |
| 138 | breadcrumb = { |
| 139 | "parent": self.tree, |
| 140 | "side": "right", |
| 141 | "left": self.tree["left"] |
| 142 | } |
| 143 | |
| 144 | return Zipper(self.tree["right"], self.breadcrumbs + [breadcrumb]) |
| 145 | |
| 22 | 146 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 147 | """ |
| 148 | Set the right child of the focus node. |
| 149 | |
| 150 | Args: |
| 151 | tree: The new right subtree (or None) |
| 152 | |
| 24 | 153 | |
| 154 | Returns: |
| 155 | A new Zipper with the updated right child |
| 156 | |
| 157 | |
| 158 | Edge Case: If the tree is None, we create a new node |
| 159 | """ |
| 160 | # Edge Case: If tree is None, create a new node |
| 161 | if self.tree is None: |
| 162 | new_tree = {"value": 0, "left": None, "right": tree} # Default value 0 |
| 163 | else: |
| 164 | new_tree = {"value": self.tree["value"], "left": self.tree["left"], "right": tree} |
| 165 | return Zipper(new_tree, self.breadcrumbs) |
| 166 | |
| 25 | 167 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 168 | """ |
| 169 | Move the focus to the parent node. |
| 170 | |
| 171 | |
| 172 | Returns: |
| 173 | A new Zipper focused on the parent, or None if at root |
| 174 | |
| 175 | |
| 176 | Edge Case: If at root (no breadcrumbs), return None |
| 177 | """ |
| 178 | # Edge Case: If at root (no breadcrumbs) |
| 179 | if not self.breadcrumbs: |
| 180 | return None |
| 181 | |
| 182 | # Get the last breadcrumb |
| 183 | parent_info = self.breadcrumbs[-1] |
| 184 | |
| 185 | # Reconstruct parent with current tree in the correct position |
| 186 | parent_tree = parent_info["parent"].copy() |
| 187 | if parent_info["side"] == "left": |
| 188 | parent_tree["left"] = self.tree |
| 189 | parent_tree["right"] = parent_info["right"] |
| 190 | else: # right |
| 191 | parent_tree["left"] = parent_info["left"] |
| 192 | parent_tree["right"] = self.tree |
| 193 | |
| 27 | 194 | |
| 195 | return Zipper(parent_tree, self.breadcrumbs[:-1]) |
| 196 | |
| 28 | 197 | def to_tree(self) -> dict: |
| 29 | | pass |
| 198 | """ |
| 199 | Get the complete tree from the zipper. |
| 200 | |
| 201 | |
| 202 | Returns: |
| 203 | The complete binary tree |
| 204 | |
| 205 | |
| 206 | Edge Case: If the tree is None, we need to reconstruct from breadcrumbs |
| 207 | """ |
| 208 | # Navigate to the root to get the complete tree |
| 209 | current = self |
| 210 | while True: |
| 211 | parent = current.up() |
| 212 | if parent is None: |
| 213 | break |
| 214 | current = parent |
| 215 | |
| 216 | # Edge Case: If the root tree is None |
| 217 | if current.tree is None: |
| 218 | return None |
| 219 | return current.tree |
| 220 | |
| 221 | # Handled Edge Cases: Empty tree, None tree, moving beyond tree boundaries, setting values on None nodes |