String Validation

Problem Statement

String Validation Problem Description You sit for a while and record part of the stream (your puzzle input). The characters represent groups - sequences that begin with { and end with }. Within a group, there are zeroes or other things, separated by commas: either another group or garbage. Since groups can contain other groups, a } only closes the most-recently-opened unclosed group - that is, they are nestable. Your puzzle input represents a single, large group containing many smaller ones. Sometimes, instead of a group, you will find garbage. Garbage begins with [ and ends with ]. Almost any character can appear between those angle brackets, including { and }. Within garbage, [ has no special meaning. In a futile attempt to clean up the garbage, some program has canceled some characters within it using !: inside the garbage, any character that comes after ! should be ignored, including [, ] and even another !. You do not see any character that deviates from these rules. Outside garba