message: Update reformat-the-string.cpp
diff: @@ -24,10 +24,8 @@ public:
  }
  string result;
  while (result.length() < s.length()) {
  - a = next_char(a, a_end, &count);
  - b = next_char(b, b_end, &count);
  - result.push_back(a);
  - result.push_back(b);
  + result.push_back(a = next_char(a, a_end, &count));
  + result.push_back(b = next_char(b, b_end, &count));
  }
  if (result.back() == '\0') {
  result.pop_back();
  