I recognized it as a variant of the classic decode-string problem pretty quickly, but the syntax difference tripped me up for a bit.
Use a stack to handle nested groups: push the current string and repeat count when encountering '{', and on '}' pop and repeat the top string, appending to the previous. Iterate through the string, building the result incrementally.
Pro tip: Clarify the input format and constraints first (e.g., whether counts are single or multi-digit, if braces are always balanced). Then discuss trade-offs between stack and recursion, and mention time/space complexity.
Ask about input format, constraints, and edge cases (e.g., nested groups, multi-digit counts, invalid input). Confirm expected output and complexity requirements.
Decide between stack and recursion. A stack is often more straightforward for iterative parsing and avoids recursion depth limits.
Outline the parsing logic: maintain a stack of (previous string, repeat count). On '{', push current state and reset; on '}', pop and repeat the current string, then append to previous.
Consider empty groups, zero repeats, multi-digit numbers, and deeply nested structures. Ensure the code handles them gracefully.
State time and space complexity: O(n * max repeat) or O(total output length) time, O(depth) space for stack.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.