| 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 | functional navigation and modification operations. |
| 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 information to navigate back up the tree |
| 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", and "right" |
| 27 | |
| 6 | 28 | |
| 29 | Returns: |
| 30 | A new Zipper instance focused on the root of the tree |
| 31 | """ |
| 32 | # Edge Case: Handle None input tree |
| 33 | if tree is None: |
| 34 | return None |
| 35 | return Zipper(tree.copy()) |
| 36 | |
| 7 | 37 | def value(self) -> int: |
| 8 | | pass |
| 38 | """ |
| 39 | Get the value of the focus node. |
| 40 | |
| 9 | 41 | |
| 42 | Returns: |
| 43 | The value of the current node |
| 44 | """ |
| 45 | # Edge Case: Handle None tree |
| 46 | if self.tree is None: |
| 47 | return None |
| 48 | return self.tree["value"] |
| 49 | |
| 10 | 50 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 51 | """ |
| 52 | Set the value of the focus node. |
| 53 | |
| 12 | 54 | |
| 55 | Args: |
| 56 | value: The new value for the focus node |
| 57 | |
| 58 | |
| 59 | Returns: |
| 60 | A new Zipper with the updated value |
| 61 | """ |
| 62 | # Edge Case: Handle None tree |
| 63 | if self.tree is None: |
| 64 | return self |
| 65 | new_tree = self.tree.copy() |
| 66 | new_tree["value"] = value |
| 67 | return Zipper(new_tree, self.breadcrumbs) |
| 68 | |
| 13 | 69 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 70 | """ |
| 71 | Move the focus to the left child of the current node. |
| 72 | |
| 15 | 73 | |
| 74 | Returns: |
| 75 | A new Zipper focused on the left child, or None if no left child exists |
| 76 | """ |
| 77 | # Edge Case: Handle None tree |
| 78 | if self.tree is None: |
| 79 | return None |
| 80 | # Edge Case: Handle missing left child |
| 81 | if self.tree["left"] is None: |
| 82 | return None |
| 83 | |
| 84 | new_breadcrumbs = self.breadcrumbs + [{ |
| 85 | "parent": self.tree, |
| 86 | "side": "left", |
| 87 | "sibling": self.tree["right"] |
| 88 | }] |
| 89 | return Zipper(self.tree["left"], new_breadcrumbs) |
| 90 | |
| 16 | 91 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 92 | """ |
| 93 | Set the left child of the focus node. |
| 94 | |
| 95 | |
| 96 | Args: |
| 97 | tree: The new left subtree (or None to remove the left child) |
| 98 | |
| 18 | 99 | |
| 100 | Returns: |
| 101 | A new Zipper with the updated left child |
| 102 | """ |
| 103 | # Edge Case: Handle None tree |
| 104 | if self.tree is None: |
| 105 | return self |
| 106 | new_tree = self.tree.copy() |
| 107 | new_tree["left"] = tree |
| 108 | return Zipper(new_tree, self.breadcrumbs) |
| 109 | |
| 19 | 110 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 111 | """ |
| 112 | Move the focus to the right child of the current node. |
| 113 | |
| 21 | 114 | |
| 115 | Returns: |
| 116 | A new Zipper focused on the right child, or None if no right child exists |
| 117 | """ |
| 118 | # Edge Case: Handle None tree |
| 119 | if self.tree is None: |
| 120 | return None |
| 121 | # Edge Case: Handle missing right child |
| 122 | if self.tree["right"] is None: |
| 123 | return None |
| 124 | |
| 125 | new_breadcrumbs = self.breadcrumbs + [{ |
| 126 | "parent": self.tree, |
| 127 | "side": "right", |
| 128 | "sibling": self.tree["left"] |
| 129 | }] |
| 130 | return Zipper(self.tree["right"], new_breadcrumbs) |
| 131 | |
| 22 | 132 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 133 | """ |
| 134 | Set the right child of the focus node. |
| 135 | |
| 136 | |
| 137 | Args: |
| 138 | tree: The new right subtree (or None to remove the right child) |
| 139 | |
| 24 | 140 | |
| 141 | Returns: |
| 142 | A new Zipper with the updated right child |
| 143 | """ |
| 144 | # Edge Case: Handle None tree |
| 145 | if self.tree is None: |
| 146 | return self |
| 147 | new_tree = self.tree.copy() |
| 148 | new_tree["right"] = tree |
| 149 | return Zipper(new_tree, self.breadcrumbs) |
| 150 | |
| 25 | 151 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 152 | """ |
| 153 | Move the focus to the parent of the current node. |
| 154 | |
| 27 | 155 | |
| 156 | Returns: |
| 157 | A new Zipper focused on the parent, or None if already at the root |
| 158 | """ |
| 159 | # Edge Case: Handle when already at root (no breadcrumbs) |
| 160 | if not self.breadcrumbs: |
| 161 | return None |
| 162 | |
| 163 | last_breadcrumb = self.breadcrumbs[-1] |
| 164 | parent = last_breadcrumb["parent"].copy() |
| 165 | |
| 166 | # Reattach the current tree to its parent |
| 167 | if last_breadcrumb["side"] == "left": |
| 168 | parent["left"] = self.tree |
| 169 | parent["right"] = last_breadcrumb["sibling"] |
| 170 | else: # right |
| 171 | parent["right"] = self.tree |
| 172 | parent["left"] = last_breadcrumb["sibling"] |
| 173 | |
| 174 | |
| 175 | return Zipper(parent, self.breadcrumbs[:-1]) |
| 176 | |
| 28 | 177 | def to_tree(self) -> dict: |
| 29 | | pass |
| 178 | """ |
| 179 | Get the complete binary tree from the zipper. |
| 180 | |
| 181 | |
| 182 | Returns: |
| 183 | The complete binary tree |
| 184 | """ |
| 185 | # Navigate back to the root to get the complete tree |
| 186 | current = self |
| 187 | while True: |
| 188 | parent = current.up() |
| 189 | if parent is None: |
| 190 | break |
| 191 | current = parent |
| 192 | return current.tree |
| 193 | |
| 194 | # Handled Edge Cases: Handle None input tree, Handle None tree in value(), Handle missing left child, Handle missing right child, Handle when already at root (no breadcrumbs) |
| 195 | # Handled Edge Cases: Handle None input tree, Handle None tree in set_value(), Handle None tree in set_left(), Handle None tree in set_right() |
| 196 | # Handled Edge Cases: Handle None tree in left(), Handle missing left child |
| 197 | # Handled Edge Cases: Handle None tree in right(), Handle missing right child |
| 198 | # Handled Edge Cases: Handle when already at root (no breadcrumbs) |
| 199 | # Handled Edge Cases: None for this method as it's a utility method that rebuilds the tree by navigating up |