[string_integer_interconversion problem] The solution in the book does not pass all test cases

[nv-quan]

The solution in the book does not check for the first '+' character, which appears in one of test cases (2/15002). And also I think the description in the book is not clear enough about all the ill-form input like "+4176473".

[MichaelBagnasco]

I ran into the same issue. Simply adding s[0] == '+' to the accumulate begin check fixes it.

Old (solution from the book)

int StringToInt(const string& s) {
  return (s[0] == '-' ? -1 : 1) * std::accumulate(std::begin(s) + (s[0] == '-'), std::end(s), 0, [](int running_sum, char c) {
    return running_sum * 10 + c - '0';
  });
}

New

int StringToInt(const string& s) {
  return (s[0] == '-' ? -1 : 1) * std::accumulate(std::begin(s) + (s[0] == '-' || s[0] == '+'), std::end(s), 0, [](int running_sum, char c) {
    return running_sum * 10 + c - '0';
  });
}