fix bug in parser

src/io/parser.cpp

@@ -112,7 +112,10 @@ std::vector<std::string> ReadKLineFromFile(const char* filename, bool header, in
   for (int i = 0; i < k; ++i) {
     if (!tmp_file.eof()) {
       GetLine(&tmp_file, &cur_line, reader.get(), &buffer, buffer_size);
+      cur_line = Common::Trim(cur_line);
+      if (!cur_line.empty()) {
         ret.push_back(cur_line);
+      }
     } else {
       break;
     }
@@ -142,7 +145,7 @@ DataType GetDataType(const std::vector<std::string>& lines, int* num_col) {
     } else if (comma_cnt > 0) {
       type = DataType::CSV;
     }
-  }
+  } else if (lines.size() > 1) {
     int comma_cnt2 = 0;
     int tab_cnt2 = 0;
     int colon_cnt2 = 0;
@@ -167,7 +170,7 @@ DataType GetDataType(const std::vector<std::string>& lines, int* num_col) {
         }
       }
     }
-
+  }
   if (type == DataType::LIBSVM) {
     int max_col_idx = 0;
     for (size_t i = 0; i < lines.size(); ++i) {