| 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 maintains a focus on a specific node in the tree, allowing for |
| 6 | functional navigation and modification. It keeps track of the path from |
| 7 | the root to the current focus node to enable upward and sibling navigation. |
| 8 | |
| 9 | Attributes: |
| 10 | _focus (dict): The current node in focus with keys 'value', 'left', 'right' |
| 11 | _path (list): List of breadcrumbs representing the path from root to focus |
| 12 | """ |
| 13 | |
| 14 | def __init__(self, focus: dict, path: list): |
| 15 | """ |
| 16 | Initialize a Zipper with a focus node and path. |
| 17 | |
| 18 | Args: |
| 19 | focus (dict): The node currently in focus |
| 20 | path (list): The path of breadcrumbs from root to focus |
| 21 | """ |
| 22 | self._focus = focus |
| 23 | self._path = path |
| 24 | |
| 3 | 25 | @staticmethod |
| 4 | 26 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 27 | """ |
| 28 | Create a zipper from a binary tree, with focus on the root node. |
| 29 | |
| 30 | Args: |
| 31 | tree (dict): A binary tree represented as a dict with keys 'value', 'left', 'right' |
| 32 | |
| 33 | Returns: |
| 34 | Zipper: A new zipper with focus on the root of the tree |
| 35 | |
| 36 | Edge Case: Empty tree (None) - Returns None |
| 37 | """ |
| 38 | # Edge Case: Empty tree |
| 39 | if tree is None: |
| 40 | return 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 | int: The value of the focus node |
| 49 | |
| 50 | Edge Case: Empty focus - Should not occur with valid zippers |
| 51 | """ |
| 52 | # Edge Case: Empty focus (should not happen with properly constructed zippers) |
| 53 | if self._focus is None: |
| 54 | return None |
| 55 | return self._focus["value"] |
| 56 | |
| 10 | 57 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 58 | """ |
| 59 | Set the value of the focus node, returning a new zipper. |
| 60 | |
| 61 | Args: |
| 62 | value (int): The new value for the focus node |
| 63 | |
| 64 | Returns: |
| 65 | Zipper: A new zipper with updated focus node value |
| 66 | """ |
| 67 | new_focus = { |
| 68 | "value": value, |
| 69 | "left": self._focus["left"], |
| 70 | "right": self._focus["right"] |
| 71 | } |
| 72 | return Zipper(new_focus, self._path) |
| 73 | |
| 13 | 74 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 75 | """ |
| 76 | Move the focus to the left child of the current focus node. |
| 77 | |
| 78 | Returns: |
| 79 | Zipper | None: A new zipper with focus on the left child, or None if no left child |
| 80 | |
| 81 | Edge Case: No left child - Returns None |
| 82 | Edge Case: Empty focus - Returns None |
| 83 | """ |
| 84 | # Edge Case: Empty focus |
| 85 | if self._focus is None: |
| 86 | return None |
| 87 | |
| 88 | # Edge Case: No left child |
| 89 | if self._focus["left"] is None: |
| 90 | return None |
| 91 | |
| 92 | # Create a breadcrumb to remember the path |
| 93 | breadcrumb = { |
| 94 | "parent": self._focus["value"], |
| 95 | "left": None, # No left subtree from parent's perspective |
| 96 | "right": self._focus["right"], |
| 97 | "rest": self._path |
| 98 | } |
| 99 | |
| 100 | return Zipper(self._focus["left"], [breadcrumb] + self._path) |
| 101 | |
| 16 | 102 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 103 | """ |
| 104 | Set the left child of the focus node, returning a new zipper. |
| 105 | |
| 106 | Args: |
| 107 | tree (dict | None): The new left subtree (or None to remove left child) |
| 108 | |
| 109 | Returns: |
| 110 | Zipper: A new zipper with updated left child |
| 111 | """ |
| 112 | new_focus = { |
| 113 | "value": self._focus["value"], |
| 114 | "left": tree, |
| 115 | "right": self._focus["right"] |
| 116 | } |
| 117 | return Zipper(new_focus, self._path) |
| 118 | |
| 19 | 119 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 120 | """ |
| 121 | Move the focus to the right child of the current focus node. |
| 122 | |
| 123 | Returns: |
| 124 | Zipper | None: A new zipper with focus on the right child, or None if no right child |
| 125 | |
| 126 | Edge Case: No right child - Returns None |
| 127 | Edge Case: Empty focus - Returns None |
| 128 | """ |
| 129 | # Edge Case: Empty focus |
| 130 | if self._focus is None: |
| 131 | return None |
| 132 | |
| 133 | # Edge Case: No right child |
| 134 | if self._focus["right"] is None: |
| 135 | return None |
| 136 | |
| 137 | # Create a breadcrumb to remember the path |
| 138 | breadcrumb = { |
| 139 | "parent": self._focus["value"], |
| 140 | "left": self._focus["left"], |
| 141 | "right": None, # No right subtree from parent's perspective |
| 142 | "rest": self._path |
| 143 | } |
| 144 | |
| 145 | return Zipper(self._focus["right"], [breadcrumb] + self._path) |
| 146 | |
| 22 | 147 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 148 | """ |
| 149 | Set the right child of the focus node, returning a new zipper. |
| 150 | |
| 151 | Args: |
| 152 | tree (dict | None): The new right subtree (or None to remove right child) |
| 153 | |
| 154 | Returns: |
| 155 | Zipper: A new zipper with updated right child |
| 156 | """ |
| 157 | new_focus = { |
| 158 | "value": self._focus["value"], |
| 159 | "left": self._focus["left"], |
| 160 | "right": tree |
| 161 | } |
| 162 | return Zipper(new_focus, self._path) |
| 163 | |
| 25 | 164 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 165 | """ |
| 166 | Move the focus to the parent of the current focus node. |
| 167 | |
| 168 | Returns: |
| 169 | Zipper | None: A new zipper with focus on the parent, or None if at root |
| 170 | |
| 171 | Edge Case: Already at root - Returns None |
| 172 | Edge Case: Empty path - Returns None |
| 173 | """ |
| 174 | # Edge Case: Already at root (empty path) |
| 175 | if not self._path: |
| 176 | return None |
| 177 | |
| 178 | # Edge Case: Empty path (should be covered by above but for safety) |
| 179 | if len(self._path) == 0: |
| 180 | return None |
| 181 | |
| 182 | # Get the most recent breadcrumb |
| 183 | breadcrumb = self._path[0] |
| 184 | |
| 185 | # Reconstruct the parent node |
| 186 | parent_node = { |
| 187 | "value": breadcrumb["parent"], |
| 188 | "left": breadcrumb["left"], |
| 189 | "right": breadcrumb["right"] |
| 190 | } |
| 191 | |
| 192 | # If we came from the left child, we need to update the left pointer |
| 193 | if breadcrumb["left"] is None: |
| 194 | parent_node["left"] = self._focus |
| 195 | # If we came from the right child, we need to update the right pointer |
| 196 | elif breadcrumb["right"] is None: |
| 197 | parent_node["right"] = self._focus |
| 198 | |
| 199 | return Zipper(parent_node, breadcrumb["rest"]) |
| 200 | |
| 28 | 201 | def to_tree(self) -> dict: |
| 29 | | pass |
| 202 | """ |
| 203 | Get the complete binary tree from the zipper. |
| 204 | |
| 205 | Returns: |
| 206 | dict: The complete binary tree |
| 207 | |
| 208 | Edge Case: Empty focus - Should not occur with valid zippers |
| 209 | """ |
| 210 | # Navigate back to the root to get the complete tree |
| 211 | current = self |
| 212 | while True: |
| 213 | parent = current.up() |
| 214 | if parent is None: |
| 215 | break |
| 216 | current = parent |
| 217 | |
| 218 | return current._focus |
| 219 | |
| 220 | # Handled Edge Cases: Empty tree, Empty focus, No left child, No right child, Already at root, Empty path |