| 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 |
| 6 | for functional navigation and modification operations. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree: dict, breadcrumbs=None): |
| 10 | """ |
| 11 | Initialize a Zipper with a tree and optional breadcrumbs. |
| 12 | |
| 13 | Args: |
| 14 | tree: A dictionary representing a binary tree node with keys 'value', 'left', and 'right' |
| 15 | breadcrumbs: A list of breadcrumb dictionaries for tracking path back to root |
| 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 dictionary representing a binary tree |
| 27 | |
| 28 | Returns: |
| 29 | A new Zipper instance focused on the root of the tree |
| 30 | |
| 31 | Edge Case: Empty tree (None) is handled by returning a Zipper with an empty tree |
| 32 | """ |
| 33 | # Edge Case: Handle None tree by creating an empty tree structure |
| 34 | if tree is None: |
| 35 | tree = {"value": 0, "left": None, "right": None} |
| 36 | return Zipper(tree) |
| 6 | 37 | |
| 7 | 38 | def value(self) -> int: |
| 8 | | pass |
| 39 | """ |
| 40 | Get the value of the focus node. |
| 41 | |
| 42 | Returns: |
| 43 | The integer value of the current node |
| 44 | |
| 45 | Edge Case: Assumes the tree structure is valid and contains a 'value' key |
| 46 | """ |
| 47 | # Edge Case: Assumes valid tree structure with 'value' key |
| 48 | return self.tree["value"] |
| 9 | 49 | |
| 10 | 50 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 51 | """ |
| 52 | Set the value of the focus node. |
| 53 | |
| 54 | Args: |
| 55 | value: The new integer value for the focus node |
| 56 | |
| 57 | Returns: |
| 58 | A new Zipper instance with the updated value |
| 59 | |
| 60 | Edge Case: Creates a new zipper to maintain immutability |
| 61 | """ |
| 62 | # Edge Case: Create new tree to maintain immutability |
| 63 | new_tree = {"value": value, "left": self.tree["left"], "right": self.tree["right"]} |
| 64 | return Zipper(new_tree, self.breadcrumbs) |
| 12 | 65 | |
| 13 | 66 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 67 | """ |
| 68 | Move the focus to the left child of the current node. |
| 69 | |
| 70 | Returns: |
| 71 | A new Zipper focused on the left child, or None if no left child exists |
| 72 | |
| 73 | Edge Case: Returns None when there is no left child |
| 74 | """ |
| 75 | # Edge Case: Return None if no left child exists |
| 76 | if 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 | "is_left": True |
| 86 | } |
| 87 | |
| 88 | return Zipper(self.tree["left"], self.breadcrumbs + [breadcrumb]) |
| 15 | 89 | |
| 16 | 90 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 91 | """ |
| 92 | Set the left child of the focus node. |
| 93 | |
| 94 | Args: |
| 95 | tree: A dictionary representing a binary tree or None |
| 96 | |
| 97 | Returns: |
| 98 | A new Zipper instance with the updated left child |
| 99 | |
| 100 | Edge Case: Creates a new zipper to maintain immutability |
| 101 | """ |
| 102 | # Edge Case: Create new tree to maintain immutability |
| 103 | new_tree = {"value": self.tree["value"], "left": tree, "right": self.tree["right"]} |
| 104 | return Zipper(new_tree, self.breadcrumbs) |
| 18 | 105 | |
| 19 | 106 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 107 | """ |
| 108 | Move the focus to the right child of the current node. |
| 109 | |
| 110 | Returns: |
| 111 | A new Zipper focused on the right child, or None if no right child exists |
| 112 | |
| 113 | Edge Case: Returns None when there is no right child |
| 114 | """ |
| 115 | # Edge Case: Return None if no right child exists |
| 116 | if self.tree["right"] is None: |
| 117 | return None |
| 118 | |
| 119 | # Create breadcrumb to remember how to reconstruct the parent |
| 120 | breadcrumb = { |
| 121 | "parent": { |
| 122 | "value": self.tree["value"], |
| 123 | "left": self.tree["left"] |
| 124 | }, |
| 125 | "is_left": False |
| 126 | } |
| 127 | |
| 128 | return Zipper(self.tree["right"], self.breadcrumbs + [breadcrumb]) |
| 21 | 129 | |
| 22 | 130 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 131 | """ |
| 132 | Set the right child of the focus node. |
| 133 | |
| 134 | Args: |
| 135 | tree: A dictionary representing a binary tree or None |
| 136 | |
| 137 | Returns: |
| 138 | A new Zipper instance with the updated right child |
| 139 | |
| 140 | Edge Case: Creates a new zipper to maintain immutability |
| 141 | """ |
| 142 | # Edge Case: Create new tree to maintain immutability |
| 143 | new_tree = {"value": self.tree["value"], "left": self.tree["left"], "right": tree} |
| 144 | return Zipper(new_tree, self.breadcrumbs) |
| 24 | 145 | |
| 25 | 146 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 147 | """ |
| 148 | Move the focus to the parent of the current node. |
| 149 | |
| 150 | Returns: |
| 151 | A new Zipper focused on the parent node, or None if already at the root |
| 152 | |
| 153 | Edge Case: Returns None when trying to move up from the root (no breadcrumbs) |
| 154 | Edge Case: Reconstructs the parent tree correctly based on whether we came from left or right |
| 155 | """ |
| 156 | # Edge Case: Return None if already at root (no breadcrumbs) |
| 157 | if not self.breadcrumbs: |
| 158 | return None |
| 159 | |
| 160 | # Get the last breadcrumb |
| 161 | breadcrumb = self.breadcrumbs[-1] |
| 162 | parent = breadcrumb["parent"] |
| 163 | is_left = breadcrumb["is_left"] |
| 164 | |
| 165 | # Reconstruct the parent tree with the current tree in the correct position |
| 166 | # Edge Case: Reconstruct parent correctly based on which child we came from |
| 167 | if is_left: |
| 168 | reconstructed_tree = { |
| 169 | "value": parent["value"], |
| 170 | "left": self.tree, |
| 171 | "right": parent["right"] |
| 172 | } |
| 173 | else: |
| 174 | reconstructed_tree = { |
| 175 | "value": parent["value"], |
| 176 | "left": parent["left"], |
| 177 | "right": self.tree |
| 178 | } |
| 179 | |
| 180 | return Zipper(reconstructed_tree, self.breadcrumbs[:-1]) |
| 27 | 181 | |
| 28 | 182 | def to_tree(self) -> dict: |
| 29 | | pass |
| 183 | """ |
| 184 | Get the complete binary tree from the zipper. |
| 185 | |
| 186 | Returns: |
| 187 | A dictionary representing the complete binary tree |
| 188 | |
| 189 | Edge Case: Reconstructs the full tree by moving up to the root |
| 190 | """ |
| 191 | # Start with the current zipper |
| 192 | current = self |
| 193 | |
| 194 | # Move up until we reach the root |
| 195 | # Edge Case: Traverse up the breadcrumb trail to reconstruct the full tree |
| 196 | while True: |
| 197 | parent = current.up() |
| 198 | if parent is None: |
| 199 | break |
| 200 | current = parent |
| 201 | |
| 202 | return current.tree |
| 203 | |
| 204 | # Handled Edge Cases: Empty tree, None children, immutability, root node navigation, tree reconstruction |