Nested Pattern String Expansion

Expand strings where parenthesized groups are followed by repeat counts in curly braces, including nested groups such as `(a(bc){2}){2}`. Requirements Input is one string inputStr. A pattern is a substring enclosed in parentheses, followed by a repeat count enclosed in curly braces. Expand each pattern by concatenating it with itself the requested number of times. Pattern-count pairs can be nested, such as (ef((ab){2}cd){2}){2}. Multi-digit counts can appear. Some inputs may contain spaces; skip irrelevant spaces if the statement permits them. Examples Input: (ab){3} Output: ababab Input: (a(bc){2}){2} Output: abcbcabcbc Notes A stack-based parser is the natural fit: keep the string accumulated before (, parse the substring up to ), read the following {number}, then repeat and append. Java candidates hit errors when comparing char to String, for example using != "}" instead of comparing against '}'. Hidden cases can stress nested groups and multi-digit repeat counts.