| 1 | 1 | class Zipper: |
| 2 | def __init__(self, tree, path): |
| 3 | self.tree = tree |
| 4 | self.path = path |
| 5 | |
| 2 | 6 | # Tree is a dict with keys "value" (int), "left" (dict or None), "right" (dict or None) |
| 3 | 7 | @staticmethod |
| 4 | 8 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 9 | # Edge Case: Empty tree input |
| 10 | if tree is None: |
| 11 | return None |
| 12 | return Zipper(tree, []) |
| 6 | 13 | |
| 7 | 14 | def value(self) -> int: |
| 8 | | pass |
| 15 | # Edge Case: Called on None zipper |
| 16 | if self.tree is None: |
| 17 | return None |
| 18 | return self.tree["value"] |
| 9 | 19 | |
| 10 | 20 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 21 | # Edge Case: Called on None zipper |
| 22 | if self.tree is None: |
| 23 | return None |
| 24 | # Create a new tree with updated value |
| 25 | new_tree = {"value": value, "left": self.tree["left"], "right": self.tree["right"]} |
| 26 | # Reconstruct the tree with the path |
| 27 | return Zipper._reconstruct_from_path(new_tree, self.path) |
| 12 | 28 | |
| 13 | 29 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 30 | # Edge Case: Called on None zipper |
| 31 | if self.tree is None: |
| 32 | return None |
| 33 | # Edge Case: No left child |
| 34 | if self.tree["left"] is None: |
| 35 | return None |
| 36 | # Create a breadcrumb to remember current node when going back up |
| 37 | breadcrumb = { |
| 38 | "parent": self.tree, |
| 39 | "side": "left", |
| 40 | "sibling": self.tree["right"] |
| 41 | } |
| 42 | new_path = self.path + [breadcrumb] |
| 43 | return Zipper(self.tree["left"], new_path) |
| 15 | 44 | |
| 16 | 45 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 46 | # Edge Case: Called on None zipper |
| 47 | if self.tree is None: |
| 48 | return None |
| 49 | # Create a new tree with updated left child |
| 50 | new_tree = {"value": self.tree["value"], "left": tree, "right": self.tree["right"]} |
| 51 | # Reconstruct the tree with the path |
| 52 | return Zipper._reconstruct_from_path(new_tree, self.path) |
| 18 | 53 | |
| 19 | 54 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 55 | # Edge Case: Called on None zipper |
| 56 | if self.tree is None: |
| 57 | return None |
| 58 | # Edge Case: No right child |
| 59 | if self.tree["right"] is None: |
| 60 | return None |
| 61 | # Create a breadcrumb to remember current node when going back up |
| 62 | breadcrumb = { |
| 63 | "parent": self.tree, |
| 64 | "side": "right", |
| 65 | "sibling": self.tree["left"] |
| 66 | } |
| 67 | new_path = self.path + [breadcrumb] |
| 68 | return Zipper(self.tree["right"], new_path) |
| 21 | 69 | |
| 22 | 70 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 71 | # Edge Case: Called on None zipper |
| 72 | if self.tree is None: |
| 73 | return None |
| 74 | # Create a new tree with updated right child |
| 75 | new_tree = {"value": self.tree["value"], "left": self.tree["left"], "right": tree} |
| 76 | # Reconstruct the tree with the path |
| 77 | return Zipper._reconstruct_from_path(new_tree, self.path) |
| 24 | 78 | |
| 25 | 79 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 80 | # Edge Case: Called on None zipper |
| 81 | if self.tree is None: |
| 82 | return None |
| 83 | # Edge Case: Already at root (no path) |
| 84 | if not self.path: |
| 85 | return None |
| 86 | # Get the last breadcrumb |
| 87 | breadcrumb = self.path[-1] |
| 88 | parent = breadcrumb["parent"] |
| 89 | side = breadcrumb["side"] |
| 90 | sibling = breadcrumb["sibling"] |
| 91 | |
| 92 | # Reconstruct parent with current tree in the correct position |
| 93 | if side == "left": |
| 94 | new_parent = {"value": parent["value"], "left": self.tree, "right": sibling} |
| 95 | else: # side == "right" |
| 96 | new_parent = {"value": parent["value"], "left": sibling, "right": self.tree} |
| 97 | |
| 98 | # Create new path without the last breadcrumb |
| 99 | new_path = self.path[:-1] |
| 100 | return Zipper(new_parent, new_path) |
| 27 | 101 | |
| 28 | 102 | def to_tree(self) -> dict: |
| 29 | | pass |
| 103 | # Edge Case: Called on None zipper |
| 104 | if self.tree is None: |
| 105 | return None |
| 106 | # Navigate up to the root and return the tree |
| 107 | current = self |
| 108 | while current.path: |
| 109 | current = current.up() |
| 110 | return current.tree |
| 111 | |
| 112 | @staticmethod |
| 113 | def _reconstruct_from_path(tree, path): |
| 114 | """Helper method to reconstruct a zipper from a tree and path""" |
| 115 | zipper = Zipper(tree, []) |
| 116 | |
| 117 | # Apply breadcrumbs in reverse order to rebuild the path |
| 118 | for breadcrumb in reversed(path): |
| 119 | parent = breadcrumb["parent"] |
| 120 | side = breadcrumb["side"] |
| 121 | sibling = breadcrumb["sibling"] |
| 122 | |
| 123 | # Create a new breadcrumb for the parent |
| 124 | if side == "left": |
| 125 | new_parent = {"value": parent["value"], "left": zipper.tree, "right": sibling} |
| 126 | new_breadcrumb = { |
| 127 | "parent": parent, |
| 128 | "side": "left", |
| 129 | "sibling": sibling |
| 130 | } |
| 131 | else: # side == "right" |
| 132 | new_parent = {"value": parent["value"], "left": sibling, "right": zipper.tree} |
| 133 | new_breadcrumb = { |
| 134 | "parent": parent, |
| 135 | "side": "right", |
| 136 | "sibling": sibling |
| 137 | } |
| 138 | |
| 139 | zipper = Zipper(new_parent, zipper.path + [new_breadcrumb]) |
| 140 | |
| 141 | return zipper |
| 142 | |
| 143 | # Handled Edge Cases: Empty tree input, Called on None zipper, No left child, No right child, Already at root (no path) |