| 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 breadcrumb dicts tracking the path to the focus |
| 16 | """ |
| 17 | self.tree = tree |
| 18 | self.breadcrumbs = breadcrumbs or [] |
| 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: A binary tree as a dict with keys "value", "left", "right" |
| 27 | |
| 28 | Returns: |
| 29 | A new Zipper instance focused on the root of the tree |
| 30 | """ |
| 31 | # Edge Case: Handle None input tree |
| 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 | The value of the current node |
| 42 | """ |
| 43 | # Edge Case: Handle None tree |
| 44 | if self.tree is None: |
| 45 | return None |
| 46 | return self.tree["value"] |
| 47 | |
| 10 | 48 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 49 | """ |
| 50 | Set the value of the focus node. |
| 51 | |
| 52 | Args: |
| 53 | value: The new value for the focus node |
| 54 | |
| 55 | Returns: |
| 56 | A new Zipper with the updated value |
| 57 | """ |
| 58 | # Edge Case: Handle None tree |
| 59 | if self.tree is None: |
| 60 | return self |
| 61 | new_tree = { |
| 62 | "value": value, |
| 63 | "left": self.tree["left"], |
| 64 | "right": self.tree["right"] |
| 65 | } |
| 66 | return Zipper(new_tree, self.breadcrumbs) |
| 67 | |
| 13 | 68 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 69 | """ |
| 70 | Move the focus to the left child of the current node. |
| 71 | |
| 72 | Returns: |
| 73 | A new Zipper focused on the left child, or None if no left child exists |
| 74 | """ |
| 75 | # Edge Case: Handle None tree |
| 76 | if self.tree is None or self.tree["left"] is None: |
| 77 | return None |
| 78 | |
| 79 | # Create breadcrumb to remember how to reconstruct the parent |
| 80 | breadcrumb = { |
| 81 | "parent": { |
| 82 | "value": self.tree["value"], |
| 83 | "right": self.tree["right"] |
| 84 | }, |
| 85 | "side": "left" |
| 86 | } |
| 87 | |
| 88 | new_breadcrumbs = [breadcrumb] + self.breadcrumbs |
| 89 | return Zipper(self.tree["left"], new_breadcrumbs) |
| 90 | |
| 16 | 91 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 92 | """ |
| 93 | Set the left child of the focus node. |
| 94 | |
| 95 | Args: |
| 96 | tree: The new left subtree (or None to remove the left child) |
| 97 | |
| 98 | Returns: |
| 99 | A new Zipper with the updated left child |
| 100 | """ |
| 101 | # Edge Case: Handle None tree |
| 102 | if self.tree is None: |
| 103 | return self |
| 104 | new_tree = { |
| 105 | "value": self.tree["value"], |
| 106 | "left": tree, |
| 107 | "right": self.tree["right"] |
| 108 | } |
| 109 | return Zipper(new_tree, self.breadcrumbs) |
| 110 | |
| 19 | 111 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 112 | """ |
| 113 | Move the focus to the right child of the current node. |
| 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 or self.tree["right"] is None: |
| 120 | return None |
| 121 | |
| 122 | # Create breadcrumb to remember how to reconstruct the parent |
| 123 | breadcrumb = { |
| 124 | "parent": { |
| 125 | "value": self.tree["value"], |
| 126 | "left": self.tree["left"] |
| 127 | }, |
| 128 | "side": "right" |
| 129 | } |
| 130 | |
| 131 | new_breadcrumbs = [breadcrumb] + self.breadcrumbs |
| 132 | return Zipper(self.tree["right"], new_breadcrumbs) |
| 133 | |
| 22 | 134 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 135 | """ |
| 136 | Set the right child of the focus node. |
| 137 | |
| 138 | Args: |
| 139 | tree: The new right subtree (or None to remove the right child) |
| 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 = { |
| 148 | "value": self.tree["value"], |
| 149 | "left": self.tree["left"], |
| 150 | "right": tree |
| 151 | } |
| 152 | return Zipper(new_tree, self.breadcrumbs) |
| 153 | |
| 25 | 154 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 155 | """ |
| 156 | Move the focus to the parent of the current node. |
| 157 | |
| 158 | Returns: |
| 159 | A new Zipper focused on the parent, or None if already at the root |
| 160 | """ |
| 161 | # Edge Case: Handle when already at root (no breadcrumbs) |
| 162 | if not self.breadcrumbs: |
| 163 | return None |
| 164 | |
| 165 | breadcrumb = self.breadcrumbs[0] |
| 166 | parent = breadcrumb["parent"] |
| 167 | side = breadcrumb["side"] |
| 168 | |
| 169 | # Reconstruct the parent tree with the current tree in the correct position |
| 170 | if side == "left": |
| 171 | new_tree = { |
| 172 | "value": parent["value"], |
| 173 | "left": self.tree, |
| 174 | "right": parent["right"] |
| 175 | } |
| 176 | else: # side == "right" |
| 177 | new_tree = { |
| 178 | "value": parent["value"], |
| 179 | "left": parent["left"], |
| 180 | "right": self.tree |
| 181 | } |
| 182 | |
| 183 | return Zipper(new_tree, self.breadcrumbs[1:]) |
| 184 | |
| 28 | 185 | def to_tree(self) -> dict: |
| 29 | | pass |
| 186 | """ |
| 187 | Get the complete binary tree from the zipper. |
| 188 | |
| 189 | Returns: |
| 190 | The complete binary tree as a dict |
| 191 | """ |
| 192 | # Navigate back to the root to get the complete tree |
| 193 | current = self |
| 194 | while True: |
| 195 | parent = current.up() |
| 196 | if parent is None: |
| 197 | break |
| 198 | current = parent |
| 199 | return current.tree |
| 200 | |
| 201 | # Handled Edge Cases: None tree input, None left/right children, Already at root when moving up |