| 1 | 1 | class Zipper: |
| 2 | | # Tree is a dict with keys "value" (int), "left" (dict or None), "right" (dict or None) |
| 2 | def __init__(self, node, path): |
| 3 | # Edge Case: Initialize with None node (should not happen in normal operation but handled for safety) |
| 4 | self._node = node |
| 5 | self._path = path |
| 6 | |
| 7 | # Edge Case: Handle empty tree (None) passed to from_tree |
| 3 | 8 | @staticmethod |
| 4 | 9 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 10 | return Zipper(tree, []) |
| 6 | 11 | |
| 12 | # Edge Case: Called on a Zipper with None node (should not normally occur) |
| 7 | 13 | def value(self) -> int: |
| 8 | | pass |
| 14 | if self._node is None: |
| 15 | raise ValueError("Cannot get value of None node") |
| 16 | return self._node["value"] |
| 9 | 17 | |
| 18 | # Edge Case: Called on a Zipper with None node |
| 10 | 19 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 20 | if self._node is None: |
| 21 | raise ValueError("Cannot set value of None node") |
| 22 | new_node = {"value": value, "left": self._node["left"], "right": self._node["right"]} |
| 23 | if not self._path: |
| 24 | return Zipper(new_node, []) |
| 25 | else: |
| 26 | # Reconstruct tree with new node |
| 27 | new_path = self._path[:] |
| 28 | new_path[-1] = new_path[-1].copy() |
| 29 | if new_path[-1]["direction"] == "left": |
| 30 | new_path[-1]["parent"]["left"] = new_node |
| 31 | else: # direction == "right" |
| 32 | new_path[-1]["parent"]["right"] = new_node |
| 33 | return Zipper(new_node, new_path) |
| 12 | 34 | |
| 35 | # Edge Case: Called on a Zipper with None node or when there's no left child |
| 13 | 36 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 37 | if self._node is None or self._node["left"] is None: |
| 38 | return None |
| 39 | breadcrumb = { |
| 40 | "parent": self._node, |
| 41 | "direction": "left", |
| 42 | "right": self._node["right"] |
| 43 | } |
| 44 | return Zipper(self._node["left"], self._path + [breadcrumb]) |
| 15 | 45 | |
| 46 | # Edge Case: Called on a Zipper with None node |
| 16 | 47 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 48 | if self._node is None: |
| 49 | raise ValueError("Cannot set left of None node") |
| 50 | new_node = {"value": self._node["value"], "left": tree, "right": self._node["right"]} |
| 51 | if not self._path: |
| 52 | return Zipper(new_node, []) |
| 53 | else: |
| 54 | # Reconstruct tree with new node |
| 55 | new_path = self._path[:] |
| 56 | new_path[-1] = new_path[-1].copy() |
| 57 | if new_path[-1]["direction"] == "left": |
| 58 | new_path[-1]["parent"]["left"] = new_node |
| 59 | else: # direction == "right" |
| 60 | new_path[-1]["parent"]["right"] = new_node |
| 61 | return Zipper(new_node, new_path) |
| 18 | 62 | |
| 63 | # Edge Case: Called on a Zipper with None node or when there's no right child |
| 19 | 64 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 65 | if self._node is None or self._node["right"] is None: |
| 66 | return None |
| 67 | breadcrumb = { |
| 68 | "parent": self._node, |
| 69 | "direction": "right", |
| 70 | "left": self._node["left"] |
| 71 | } |
| 72 | return Zipper(self._node["right"], self._path + [breadcrumb]) |
| 21 | 73 | |
| 74 | # Edge Case: Called on a Zipper with None node |
| 22 | 75 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 76 | if self._node is None: |
| 77 | raise ValueError("Cannot set right of None node") |
| 78 | new_node = {"value": self._node["value"], "left": self._node["left"], "right": tree} |
| 79 | if not self._path: |
| 80 | return Zipper(new_node, []) |
| 81 | else: |
| 82 | # Reconstruct tree with new node |
| 83 | new_path = self._path[:] |
| 84 | new_path[-1] = new_path[-1].copy() |
| 85 | if new_path[-1]["direction"] == "left": |
| 86 | new_path[-1]["parent"]["left"] = new_node |
| 87 | else: # direction == "right" |
| 88 | new_path[-1]["parent"]["right"] = new_node |
| 89 | return Zipper(new_node, new_path) |
| 24 | 90 | |
| 91 | # Edge Case: Called when already at the root (no path) |
| 25 | 92 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 93 | if not self._path: |
| 94 | return None |
| 95 | |
| 96 | parent_breadcrumb = self._path[-1] |
| 97 | parent_node = parent_breadcrumb["parent"].copy() |
| 98 | |
| 99 | if parent_breadcrumb["direction"] == "left": |
| 100 | parent_node["left"] = self._node |
| 101 | parent_node["right"] = parent_breadcrumb["right"] |
| 102 | else: # direction == "right" |
| 103 | parent_node["left"] = parent_breadcrumb["left"] |
| 104 | parent_node["right"] = self._node |
| 105 | |
| 106 | return Zipper(parent_node, self._path[:-1]) |
| 27 | 107 | |
| 108 | # Edge Case: Called on a Zipper with None node |
| 28 | 109 | def to_tree(self) -> dict: |
| 29 | | pass |
| 110 | if self._node is None: |
| 111 | raise ValueError("Cannot convert None node to tree") |
| 112 | |
| 113 | # Navigate back to root |
| 114 | current = self |
| 115 | while True: |
| 116 | parent = current.up() |
| 117 | if parent is None: |
| 118 | break |
| 119 | current = parent |
| 120 | return current._node |
| 121 | |
| 122 | # Handled Edge Cases: Empty tree, None node operations, moving when no child exists, setting on None node, already at root |