| 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, allowing for |
| 6 | efficient navigation and modification operations. |
| 7 | """ |
| 8 | def __init__(self, tree, path): |
| 9 | """ |
| 10 | Initialize a Zipper. |
| 11 | |
| 12 | Args: |
| 13 | tree: The complete tree structure |
| 14 | path: A list of tuples representing the path from root to focus node. |
| 15 | Each tuple contains (parent_node, side) where side is 'left' or 'right' |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.path = path |
| 19 | |
| 20 | # Calculate the focus node based on the path |
| 21 | self.focus = tree |
| 22 | for parent, side in self.path: |
| 23 | if self.focus is None: |
| 24 | break |
| 25 | self.focus = self.focus.get(side) |
| 26 | |
| 3 | 27 | @staticmethod |
| 4 | 28 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 29 | """ |
| 30 | Create a zipper from a binary tree. |
| 31 | |
| 32 | Args: |
| 33 | tree: A binary tree represented as a dict with keys "value", "left", and "right" |
| 34 | |
| 35 | Returns: |
| 36 | A new Zipper instance with focus on the root node |
| 37 | """ |
| 38 | # Edge Case: Handle None tree input |
| 39 | if tree is None: |
| 40 | return Zipper(None, []) |
| 41 | return Zipper(tree, []) |
| 42 | |
| 7 | 43 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 44 | """ |
| 45 | Get the value of the focus node. |
| 46 | |
| 47 | Returns: |
| 48 | The value of the focus node |
| 49 | |
| 50 | Raises: |
| 51 | Exception: If the focus is None (empty tree) |
| 52 | """ |
| 53 | # Edge Case: Handle when focus is None |
| 54 | if self.focus is None: |
| 55 | raise Exception("Cannot get value of None focus") |
| 56 | return self.focus["value"] |
| 57 | |
| 10 | 58 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 59 | """ |
| 60 | Set the value of the focus node. |
| 61 | |
| 62 | Args: |
| 63 | value: The new value for the focus node |
| 64 | |
| 65 | Returns: |
| 66 | A new Zipper instance with the updated value |
| 67 | """ |
| 68 | # Edge Case: Handle when focus is None |
| 69 | if self.focus is None: |
| 70 | raise Exception("Cannot set value of None focus") |
| 71 | |
| 72 | # Create a new tree with the updated value |
| 73 | new_tree = self._copy_tree(self.tree) |
| 74 | |
| 75 | # Navigate to the focus node in the new tree |
| 76 | current = new_tree |
| 77 | for parent, side in self.path: |
| 78 | current = current[side] |
| 79 | |
| 80 | # Update the value |
| 81 | current["value"] = value |
| 82 | |
| 83 | return Zipper(new_tree, self.path) |
| 84 | |
| 13 | 85 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 86 | """ |
| 87 | Move the focus to the left child of the current focus node. |
| 88 | |
| 89 | Returns: |
| 90 | A new Zipper instance focused on the left child, or None if no left child exists |
| 91 | """ |
| 92 | # Edge Case: Handle when focus is None |
| 93 | if self.focus is None or self.focus.get("left") is None: |
| 94 | return None |
| 95 | |
| 96 | # Create a new path with the current focus added |
| 97 | new_path = self.path + [(self.focus, "left")] |
| 98 | return Zipper(self.tree, new_path) |
| 99 | |
| 16 | 100 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 101 | """ |
| 102 | Set the left child of the focus node. |
| 103 | |
| 104 | Args: |
| 105 | tree: The new left subtree (or None to remove the left child) |
| 106 | |
| 107 | Returns: |
| 108 | A new Zipper instance with the updated left child |
| 109 | """ |
| 110 | # Edge Case: Handle when focus is None |
| 111 | if self.focus is None: |
| 112 | raise Exception("Cannot set left of None focus") |
| 113 | |
| 114 | # Create a new tree with the updated left child |
| 115 | new_tree = self._copy_tree(self.tree) |
| 116 | |
| 117 | # Navigate to the focus node in the new tree |
| 118 | current = new_tree |
| 119 | for parent, side in self.path: |
| 120 | current = current[side] |
| 121 | |
| 122 | # Update the left child |
| 123 | current["left"] = tree |
| 124 | |
| 125 | return Zipper(new_tree, self.path) |
| 126 | |
| 19 | 127 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 128 | """ |
| 129 | Move the focus to the right child of the current focus node. |
| 130 | |
| 131 | Returns: |
| 132 | A new Zipper instance focused on the right child, or None if no right child exists |
| 133 | """ |
| 134 | # Edge Case: Handle when focus is None |
| 135 | if self.focus is None or self.focus.get("right") is None: |
| 136 | return None |
| 137 | |
| 138 | # Create a new path with the current focus added |
| 139 | new_path = self.path + [(self.focus, "right")] |
| 140 | return Zipper(self.tree, new_path) |
| 141 | |
| 22 | 142 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 143 | """ |
| 144 | Set the right child of the focus node. |
| 145 | |
| 146 | Args: |
| 147 | tree: The new right subtree (or None to remove the right child) |
| 148 | |
| 149 | Returns: |
| 150 | A new Zipper instance with the updated right child |
| 151 | """ |
| 152 | # Edge Case: Handle when focus is None |
| 153 | if self.focus is None: |
| 154 | raise Exception("Cannot set right of None focus") |
| 155 | |
| 156 | # Create a new tree with the updated right child |
| 157 | new_tree = self._copy_tree(self.tree) |
| 158 | |
| 159 | # Navigate to the focus node in the new tree |
| 160 | current = new_tree |
| 161 | for parent, side in self.path: |
| 162 | current = current[side] |
| 163 | |
| 164 | # Update the right child |
| 165 | current["right"] = tree |
| 166 | |
| 167 | return Zipper(new_tree, self.path) |
| 168 | |
| 25 | 169 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 170 | """ |
| 171 | Move the focus to the parent of the current focus node. |
| 172 | |
| 173 | Returns: |
| 174 | A new Zipper instance focused on the parent, or None if at the root |
| 175 | """ |
| 176 | # Edge Case: Handle when at root (no parent) |
| 177 | if len(self.path) == 0: |
| 178 | return None |
| 179 | |
| 180 | # Create a new path without the last element |
| 181 | new_path = self.path[:-1] |
| 182 | return Zipper(self.tree, new_path) |
| 183 | |
| 28 | 184 | def to_tree(self) -> dict: |
| 29 | | pass |
| 185 | """ |
| 186 | Get the complete tree from the zipper. |
| 187 | |
| 188 | Returns: |
| 189 | The complete binary tree |
| 190 | """ |
| 191 | return self.tree |
| 192 | |
| 193 | def _copy_tree(self, tree): |
| 194 | """ |
| 195 | Create a deep copy of a binary tree. |
| 196 | |
| 197 | Args: |
| 198 | tree: The tree to copy |
| 199 | |
| 200 | Returns: |
| 201 | A deep copy of the tree |
| 202 | """ |
| 203 | if tree is None: |
| 204 | return None |
| 205 | |
| 206 | return { |
| 207 | "value": tree["value"], |
| 208 | "left": self._copy_tree(tree.get("left")), |
| 209 | "right": self._copy_tree(tree.get("right")) |
| 210 | } |
| 211 | |
| 212 | # Handled Edge Cases: None tree input, None focus, setting/getting value of None focus, |
| 213 | # moving left/right when no child exists, moving up when at root |