Implement a C++ class, constructed from an istream, whose begin() and end() return input iterators over the valid integers in a file of one value per line.

A file holds integers one per line. Implement a C++ class Solution, constructed from an istream, that exposes begin() and end() returning input iterators over the valid integers. A valid line is an optional sign followed by digits without leading zeros, in the range [-1,000,000,000, 1,000,000,000], with optional spaces before and after; any other line (e.g. '2u1', '23.9', '#12', '00', '++1', '2000000000') is a comment and must be skipped.