## Problem Implement a code folding engine for a source code editor. Given source code as a list of lines, detect foldable regions (blocks delimited by `{` and `}`, or by indentation for Python-style code), and support fold/unfold operations. ```python class CodeFolder: def __init__(self, lines: list[str], style: str = "brace"): # style: "brace"|"indent" def get_foldable_ranges(self) -> list[tuple[int, int]]: # (start_line, end_line) def fold(self, start_line: int) -> list[str]: # returns visible lines def unfold(self, start_line: int) -> list[str]: def fold_all(self) -> list[str]: ``` ## Example ``` lines = [ "function foo() {", # line 0 - foldable range (0, 3) " if (x) {", # line 1 - foldable range (1, 2) " return x;", # line 2 " }", # line 3 "}", # line 4 ] get_foldable_ranges() -> [(0, 4), (1, 3)] fold(0) -> ["function foo() { ... }", "}"] ``` ## Follow-ups 1. How do you handle mismatched braces in malformed source code? 2. What data structure efficiently tracks nested folds as the user types? 3. How would you extend this to support language-specific fold points (e.g., `if/else`, `try/catch`)?

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Code Folding: Implement Code Block Detection and Folding for a Text Editor

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Problem Implement a code folding engine for a source code editor. Given source code as a list of lines, detect foldable regions (blocks delimited by { and }, or by indentation for Python-style code), and support fold/unfold operations. Example Follow-ups How do you handle mismatched braces in malformed source code? What data structure efficiently tracks nested folds as the user types? How would you extend this to support language-specific fold points (e.g., if/else, try/catch)?

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Code Folding: Implement Code Block Detection and Folding for a Text Editor

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