diff --git a/src/KeyWordExt.cpp b/src/KeyWordExt.cpp
index 6499d11..7eaaaf7 100644
--- a/src/KeyWordExt.cpp
+++ b/src/KeyWordExt.cpp
@@ -23,11 +23,175 @@ namespace CppJieba
 		return true;
 	}
 
-	bool KeyWordExt::extract(const string& utf8Str)
+	bool KeyWordExt::_pair_compare(const pair<string, double>& a, const pair<string, double>& b)
 	{
+		return a.second < b.second;
+	}
+	bool KeyWordExt::_extractTopN(const vector<string>& words, vector<string>& keywords, uint topN)
+	{
+		keywords.clear();
+		vector<pair<string, double> > tmp;
+
+		for(uint i = 0; i < words.size(); i++)
+		{
+			double w = _segment.getUtf8WordWeight(words[i]);
+			tmp.push_back(pair<string, double>(words[i], w));
+		}
+		
+		sort(tmp.begin(), tmp.end(), _pair_compare);
+
+		//logging result
+		vector<string> logBuf;//for LogDebug
+		for(uint i = 0; i < tmp.size(); i++)
+		{
+			logBuf.push_back(string_format("(%s,%lf)", tmp[i].first.c_str(), tmp[i].second));
+		}
+		LogDebug(string_format("calc weight:%s",joinStr(logBuf, ",").c_str()));
+		
+		//extract TopN
+		for(uint i = 0; i < topN && i < tmp.size(); i++)
+		{
+			keywords.push_back(tmp[i].first);
+		}
+		return true;
+	}
+
+	bool KeyWordExt::extract(const string& utf8Str, vector<string>& keywords, uint topN)
+	{
+		LogInfo(utf8Str);
+		bool retFlag;
+		vector<string> tmp;
+		retFlag = _segment.cutDAG(utf8Str, tmp);
+		if(!retFlag)
+		{
+			LogError(string_format("cutDAG(%s) failed.", utf8Str.c_str()));
+			return false;
+		}
+		// like str.join([]) in python
+		LogDebug(string_format("cutDAG result:[%s]", joinStr(tmp, ",").c_str()));
+
+		retFlag = _filter(tmp);
+		if(!retFlag)
+		{
+			LogError("_filter failed.");
+			return false;
+		}
+		LogDebug(string_format("_filter res:[%s]", joinStr(tmp, ",").c_str()));
+
+		retFlag = _extractTopN(tmp, keywords, topN);
+		if(!retFlag)
+		{
+			LogError("_extractTopN failed.");
+			return false;
+		}
+		LogDebug("_extractTopN finished.");
+
+		LogInfo(string_format("ext res:[%s]", joinStr(keywords, ",").c_str()));
+		return true;
+	}
+
+	bool KeyWordExt::_filter(vector<string>& utf8Strs)
+	{
+		bool retFlag;
+		retFlag = _filterDuplicate(utf8Strs);
+		if(!retFlag)
+		{
+			LogError("_filterDuplicate failed.");
+			return false;
+		}
+		LogDebug(string_format("_filterDuplicate res:[%s]", joinStr(utf8Strs, ",").c_str()));
+
+		retFlag = _filterSingleWord(utf8Strs);
+		if(!retFlag)
+		{
+			LogError("_filterSingleWord failed.");
+			return false;
+		}
+		LogDebug(string_format("_filterSingleWord res:[%s]", joinStr(utf8Strs, ",").c_str()));
+
+		retFlag = _filterSubstr(utf8Strs);
+		if(!retFlag)
+		{
+			LogError("_filterSubstr failed.");
+			return false;
+		}
+		LogDebug(string_format("_filterSubstr res:[%s]", joinStr(utf8Strs, ",").c_str()));
+
+		return true;
+	}
+
+	bool KeyWordExt::_filterDuplicate(vector<string>& utf8Strs)
+	{
+		set<string> st;
+		for(VSI it = utf8Strs.begin(); it != utf8Strs.end(); )
+		{
+			if(st.find(*it) != st.end())
+			{
+				it = utf8Strs.erase(it);
+			}
+			else
+			{
+				st.insert(*it);
+				it++;
+			}
+		}
+		return true;
+	}
+
+	bool KeyWordExt::_filterSingleWord(vector<string>& utf8Strs)
+	{
+		for(vector<string>::iterator it = utf8Strs.begin(); it != utf8Strs.end();)
+		{
+			string uniStr = utf8ToUnicode(*it);
+			if(uniStr.empty() || uniStr.size()%2)
+			{
+				LogError("utf8ToUnicode error");
+				return false;
+			}
+
+			// filter single word
+			if(uniStr.size() == 2) 
+			{
+				it = utf8Strs.erase(it);
+			}
+			else
+			{
+				it++;
+			}
+		}
+		return true;
+	}
+
+	bool KeyWordExt::_filterSubstr(vector<string>& utf8Strs)
+	{
+		vector<string> tmp = utf8Strs;
+		set<string> subs;
+		for(VSI it = utf8Strs.begin(); it != utf8Strs.end(); it ++)
+		{
+			for(uint j = 0; j < tmp.size(); j++)
+			{
+				if(*it != tmp[j] && string::npos != tmp[j].find(*it, 0))
+				{
+					subs.insert(*it);
+				}
+			}
+		}
+
+		//erase subs from utf8Strs
+		for(VSI it = utf8Strs.begin(); it != utf8Strs.end(); )
+		{
+			if(subs.end() != subs.find(*it))
+			{
+				LogDebug(string_format("_filterSubstr filter [%s].", it->c_str()));
+				it =  utf8Strs.erase(it);
+			}
+			else
+			{
+				it ++;
+			}
+		}
 		return true;
 	}
-	
 }
 
 
@@ -38,6 +202,35 @@ using namespace CppJieba;
 int main()
 {
 	KeyWordExt ext;
+	if(!ext.init("../dicts/segdict.utf8.v2.1"))
+	{
+		return 1;
+	}
+	//segment.init("dicts/jieba.dict.utf8");
+	
+	vector<string> res;
+	string title;
+	title = "我来到北京清华大学";
+	res.clear();
+	ext.extract(title, res, 5);
+	PRINT_VECTOR(res);
+	
+	title = "特价！camel骆驼 柔软舒适头层牛皮平底凉鞋女 休闲平跟妈妈鞋夏";
+	res.clear();
+	ext.extract(title, res, 5);
+	PRINT_VECTOR(res);
+
+	title = "包邮拉菲草18cm大檐进口草帽子超强遮阳防晒欧美日韩新款夏天 女";
+	res.clear();
+	ext.extract(title, res, 5);
+	PRINT_VECTOR(res);
+
+	title = "2013新款19CM超大檐帽 遮阳草帽子 沙滩帽防晒大檐欧美新款夏天女";
+	res.clear();
+	ext.extract(title, res, 5);
+	PRINT_VECTOR(res);
+
+	ext.destroy();
 	return 0;
 }
 
diff --git a/src/KeyWordExt.h b/src/KeyWordExt.h
index b4fbde8..cb5fbf7 100644
--- a/src/KeyWordExt.h
+++ b/src/KeyWordExt.h
@@ -16,7 +16,14 @@ namespace CppJieba
 			bool destroy();
 
 		public:
-			bool extract(const string& utf8Str);
+			bool extract(const string& utf8Str, vector<string>& keywords, uint topN);
+		private:
+			static bool _pair_compare(const pair<string, double>& a, const pair<string, double>& b);
+			bool _extractTopN(const vector<string>& words, vector<string>& keywords, uint topN);
+			bool _filter(vector<string>& utf8Strs);
+			bool _filterDuplicate(vector<string>& utf8Strs);
+			bool _filterSingleWord(vector<string>& utf8Strs);
+			bool _filterSubstr(vector<string>& utf8Strs);
 
 	};
 
diff --git a/src/Segment.cpp b/src/Segment.cpp
index 9a4520e..685f220 100644
--- a/src/Segment.cpp
+++ b/src/Segment.cpp
@@ -64,39 +64,6 @@ namespace CppJieba
 		
 		return true;
 	}
-	bool Segment::extract(const string& utf8Str, vector<string>& keywords, uint topN)
-	{
-		LogInfo(utf8Str);
-		bool retFlag;
-		vector<string> tmp;
-		retFlag = cutDAG(utf8Str, tmp);
-		if(!retFlag)
-		{
-			LogError(string_format("cutDAG(%s) failed.", utf8Str.c_str()));
-			return false;
-		}
-		// like str.join([]) in python
-		LogDebug(string_format("cutDAG result:[%s]", joinStr(tmp, ",").c_str()));
-
-		retFlag = _filter(tmp);
-		if(!retFlag)
-		{
-			LogError("_filter failed.");
-			return false;
-		}
-		LogDebug(string_format("_filter res:[%s]", joinStr(tmp, ",").c_str()));
-
-		retFlag = _extractTopN(tmp, keywords, topN);
-		if(!retFlag)
-		{
-			LogError("_extractTopN failed.");
-			return false;
-		}
-		LogDebug("_extractTopN finished.");
-
-		LogInfo(string_format("ext res:[%s]", joinStr(keywords, ",").c_str()));
-		return true;
-	}
 
 	double Segment::getUtf8WordWeight(const string& word)
 	{
@@ -108,39 +75,7 @@ namespace CppJieba
 		return _trie.getWeight(word);
 	}
 
-	bool Segment::_pair_compare(const pair<string, double>& a, const pair<string, double>& b)
-	{
-		return a.second < b.second;
-	}
 
-	bool Segment::_extractTopN(const vector<string>& words, vector<string>& keywords, uint topN)
-	{
-		keywords.clear();
-		vector<pair<string, double> > tmp;
-
-		for(uint i = 0; i < words.size(); i++)
-		{
-			double w = getUtf8WordWeight(words[i]);
-			tmp.push_back(pair<string, double>(words[i], w));
-		}
-		
-		sort(tmp.begin(), tmp.end(), _pair_compare);
-
-		//logging result
-		vector<string> logBuf;//for LogDebug
-		for(uint i = 0; i < tmp.size(); i++)
-		{
-			logBuf.push_back(string_format("(%s,%lf)", tmp[i].first.c_str(), tmp[i].second));
-		}
-		LogDebug(string_format("calc weight:%s",joinStr(logBuf, ",").c_str()));
-		
-		//extract TopN
-		for(uint i = 0; i < topN && i < tmp.size(); i++)
-		{
-			keywords.push_back(tmp[i].first);
-		}
-		return true;
-	}
 
 	string Segment::_utf8ToUni(const string& utfStr)
 	{
@@ -243,108 +178,6 @@ namespace CppJieba
 		return true;
 	}
 
-	bool Segment::_filter(vector<string>& utf8Strs)
-	{
-		bool retFlag;
-		retFlag = _filterDuplicate(utf8Strs);
-		if(!retFlag)
-		{
-			LogError("_filterDuplicate failed.");
-			return false;
-		}
-		LogDebug(string_format("_filterDuplicate res:[%s]", joinStr(utf8Strs, ",").c_str()));
-
-		retFlag = _filterSingleWord(utf8Strs);
-		if(!retFlag)
-		{
-			LogError("_filterSingleWord failed.");
-			return false;
-		}
-		LogDebug(string_format("_filterSingleWord res:[%s]", joinStr(utf8Strs, ",").c_str()));
-
-		retFlag = _filterSubstr(utf8Strs);
-		if(!retFlag)
-		{
-			LogError("_filterSubstr failed.");
-			return false;
-		}
-		LogDebug(string_format("_filterSubstr res:[%s]", joinStr(utf8Strs, ",").c_str()));
-
-		return true;
-	}
-
-	bool Segment::_filterDuplicate(vector<string>& utf8Strs)
-	{
-		set<string> st;
-		for(VSI it = utf8Strs.begin(); it != utf8Strs.end(); )
-		{
-			if(st.find(*it) != st.end())
-			{
-				it = utf8Strs.erase(it);
-			}
-			else
-			{
-				st.insert(*it);
-				it++;
-			}
-		}
-		return true;
-	}
-
-	bool Segment::_filterSingleWord(vector<string>& utf8Strs)
-	{
-		for(vector<string>::iterator it = utf8Strs.begin(); it != utf8Strs.end();)
-		{
-			string uniStr = utf8ToUnicode(*it);
-			if(uniStr.empty() || uniStr.size()%2)
-			{
-				LogError("utf8ToUnicode error");
-				return false;
-			}
-
-			// filter single word
-			if(uniStr.size() == 2) 
-			{
-				it = utf8Strs.erase(it);
-			}
-			else
-			{
-				it++;
-			}
-		}
-		return true;
-	}
-
-	bool Segment::_filterSubstr(vector<string>& utf8Strs)
-	{
-		vector<string> tmp = utf8Strs;
-		set<string> subs;
-		for(VSI it = utf8Strs.begin(); it != utf8Strs.end(); it ++)
-		{
-			for(uint j = 0; j < tmp.size(); j++)
-			{
-				if(*it != tmp[j] && string::npos != tmp[j].find(*it, 0))
-				{
-					subs.insert(*it);
-				}
-			}
-		}
-
-		//erase subs from utf8Strs
-		for(VSI it = utf8Strs.begin(); it != utf8Strs.end(); )
-		{
-			if(subs.end() != subs.find(*it))
-			{
-				LogDebug(string_format("_filterSubstr filter [%s].", it->c_str()));
-				it =  utf8Strs.erase(it);
-			}
-			else
-			{
-				it ++;
-			}
-		}
-		return true;
-	}
 
 }
 
@@ -366,19 +199,23 @@ int main()
 	string title;
 	title = "我来到北京清华大学";
 	res.clear();
-	segment.extract(title, res, 5);
+	segment.cutDAG(title, res);
+	PRINT_VECTOR(res);
 	
 	title = "特价！camel骆驼 柔软舒适头层牛皮平底凉鞋女 休闲平跟妈妈鞋夏";
 	res.clear();
-	segment.extract(title, res, 5);
+	segment.cutDAG(title, res);
+	PRINT_VECTOR(res);
 
 	title = "包邮拉菲草18cm大檐进口草帽子超强遮阳防晒欧美日韩新款夏天 女";
 	res.clear();
-	segment.extract(title, res, 5);
+	segment.cutDAG(title, res);
+	PRINT_VECTOR(res);
 
 	title = "2013新款19CM超大檐帽 遮阳草帽子 沙滩帽防晒大檐欧美新款夏天女";
 	res.clear();
-	segment.extract(title, res, 5);
+	segment.cutDAG(title, res);
+	PRINT_VECTOR(res);
 
 	segment.destroy();
 	return 0;
diff --git a/src/Segment.h b/src/Segment.h
index 892331c..d7dc2fb 100644
--- a/src/Segment.h
+++ b/src/Segment.h
@@ -20,7 +20,6 @@ namespace CppJieba
 			bool destroy();
 		public:
 			bool cutDAG(const string& chStr, vector<string>& res);
-			bool extract(const string& utf8Str, vector<string>& keywords, uint topN);
 			double getUtf8WordWeight(const string& word);
 			double getUniWordWeight(const string& word);
 
@@ -29,12 +28,6 @@ namespace CppJieba
 			bool _calcDAG(const string& uniStr, vector<vector<uint> >& dag);
 			bool _calcDP(const string& uniStr, const vector<vector<uint> >& dag, vector<pair<int, double> >& res);
 			bool _cutDAG(const string& uniStr, const vector<pair<int, double> >& dp, vector<string>& res);
-			bool _filter(vector<string>& utf8Strs);
-			bool _filterDuplicate(vector<string>& utf8Strs);
-			bool _filterSingleWord(vector<string>& utf8Strs);
-			bool _filterSubstr(vector<string>& utf8Strs);
-			static bool _pair_compare(const pair<string, double>& a, const pair<string, double>& b);
-			bool _extractTopN(const vector<string>& words, vector<string>& keywords, uint topN);
 
 		private:
 			enum {bufSize = 1024};