diff --git a/src/HMMSegment.hpp b/src/HMMSegment.hpp
index e0d1267..cbe9e59 100644
--- a/src/HMMSegment.hpp
+++ b/src/HMMSegment.hpp
@@ -105,7 +105,7 @@ namespace CppJieba
             bool _cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<Unicode>& res) const 
             {
                 assert(_getInitFlag());
-                vector<size_t> status(end - begin); 
+                vector<size_t> status; 
                 if(!_viterbi(begin, end, status))
                 {
                     LogError("_viterbi failed.");
@@ -134,16 +134,18 @@ namespace CppJieba
                     return false;
                 }
                 vector<Unicode> words;
+                words.reserve(end - begin);
                 if(!cut(begin, end, words))
                 {
                     return false;
                 }
-                string tmp;
+                size_t offset = res.size();
+                res.resize(res.size() + words.size());
                 for(size_t i = 0; i < words.size(); i++)
                 {
-                    if(TransCode::encode(words[i], tmp))
+                    if(!TransCode::encode(words[i], res[offset + i]))
                     {
-                        res.push_back(tmp);
+                        LogError("encode failed.");
                     }
                 }
                 return true;
@@ -159,7 +161,7 @@ namespace CppJieba
 
                 size_t Y = STATUS_SUM;
                 size_t X = end - begin;
-                assert(status.size() == X);
+
                 size_t XYSize = X * Y;
                 size_t now, old, stat;
                 double tmp, endE, endS;
@@ -210,6 +212,7 @@ namespace CppJieba
                     stat = S;
                 }
 
+                status.resize(X);
                 for(int x = X -1 ; x >= 0; x--)
                 {
                     status[x] = stat;
diff --git a/src/MixSegment.hpp b/src/MixSegment.hpp
index c3b5ca5..f6854b8 100644
--- a/src/MixSegment.hpp
+++ b/src/MixSegment.hpp
@@ -99,9 +99,8 @@ namespace CppJieba
             virtual bool cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<string>& res)const
             {
                 assert(_getInitFlag());
-                if(begin >= end)
+                if(begin == end)
                 {
-                    LogError("begin >= end");
                     return false;
                 }
 
@@ -109,7 +108,6 @@ namespace CppJieba
                 uRes.reserve(end - begin);
                 if (!cut(begin, end, uRes))
                 {
-                    LogError("get unicode cut result error.");
                     return false;
                 }
 
diff --git a/src/SegmentBase.hpp b/src/SegmentBase.hpp
index 226a3d6..b612e54 100644
--- a/src/SegmentBase.hpp
+++ b/src/SegmentBase.hpp
@@ -39,7 +39,7 @@ namespace CppJieba
 
         public:
             virtual bool cut(Unicode::const_iterator begin, Unicode::const_iterator end, vector<string>& res) const = 0;
-            virtual bool cut(const string& str, vector<string>& res)const
+            virtual bool cut(const string& str, vector<string>& res) const
             {
                 assert(_getInitFlag());
                 res.clear();
@@ -51,10 +51,9 @@ namespace CppJieba
                 TransCode::decode(str, unicode);
                 
                 Unicode::const_iterator left = unicode.begin();
-                Unicode::const_iterator right = unicode.begin();
+                Unicode::const_iterator right;
                 
-                string oneword;
-                while(right != unicode.end())
+                for(right = unicode.begin(); right != unicode.end(); right++)
                 {
                     if(isIn(_specialSymbols, *right))
                     {
@@ -62,14 +61,9 @@ namespace CppJieba
                         {
                             cut(left, right, res);
                         }
-                        TransCode::encode(right, right + 1, oneword);
-                        res.push_back(oneword);
-                        right ++;
-                        left = right;
-                    }
-                    else
-                    {
-                        right ++;
+                        res.resize(res.size() + 1);
+                        TransCode::encode(right, right + 1, res.back());
+                        left = right + 1;
                     }
                 }
                 if(left != right)