diff --git a/simple_ir/Dic.cpp b/simple_ir/Dic.cpp
index 791279f..8ee1302 100644
--- a/simple_ir/Dic.cpp
+++ b/simple_ir/Dic.cpp
@@ -18,7 +18,7 @@ bool compareLists(List list1, List list2)
     return (list1.getTerm() < list2.getTerm());
 }
 
-List* Dic::getListByTerm(string term)
+shared_ptr<List> Dic::getListByTerm(string term)
 {
     if(!sorted)
     {
@@ -29,7 +29,7 @@ List* Dic::getListByTerm(string term)
     // Binary search
     auto results = equal_range(lists.begin(), lists.end(), searchFor, compareLists);
     if(results.first != lists.end())
-        return &(*results.first);
+        return shared_ptr<List>(&(*results.first));
     return NULL;
 }
 
@@ -40,6 +40,12 @@ void Dic::addList(string term)
     sorted = false;
 }
 
+void Dic::addList(string term, List list)
+{
+    this->lists.push_back(list);
+    sorted = false;
+}
+
 
 void Dic::sortLists()
 {
diff --git a/simple_ir/Dic.h b/simple_ir/Dic.h
index 8334838..d4cb145 100644
--- a/simple_ir/Dic.h
+++ b/simple_ir/Dic.h
@@ -4,6 +4,7 @@
 #include"Posting.h"
 #include <string>
 #include <vector>
+#include <memory>
 
 using namespace std;
 
@@ -11,9 +12,12 @@ class Dic
 {
 private:
     vector<List> lists;
+    bool sorted;
 public:
     Dic();
-    List* getListByTerm(string term);
+    shared_ptr<List> getListByTerm(string term);
     void addList(string term);
+    void addList(string term, List list);
+    void sortLists();
 };
 #endif
diff --git a/simple_ir/IndexConstructor.cpp b/simple_ir/IndexConstructor.cpp
new file mode 100644
index 0000000..22c21ca
--- /dev/null
+++ b/simple_ir/IndexConstructor.cpp
@@ -0,0 +1,70 @@
+#include "IndexConstructor.h"
+#include <boost/filesystem.hpp>
+#include "TokenReader.h"
+#include <sstream>
+#include <memory>
+#include <unordered_map>
+
+using namespace std;
+using namespace boost::filesystem;
+IndexConstructor::IndexConstructor(string folderName, int fileLimit)
+{
+    // Currently we only deal with the Reuter files 
+    if ( !exists( folderName ) ) 
+        cout << "folder " << folderName << "doesn't exit!" << endl;
+    directory_iterator end_itr; 
+    int i = 0;
+    for ( directory_iterator itr( folderName );
+        itr != end_itr && i != fileLimit;
+        ++itr, ++i )
+    {
+        if ( is_regular_file(itr->status()) )
+        {
+            files.push_back(itr->path().string());
+        }
+    }
+    cout << "Done getting all file names. " << files.size() << " files in total." << endl;
+}
+
+int IndexConstructor::getFileId(string fileName)
+{
+    // Assume files are named as numbers
+    string idStr = boost::filesystem::path(fileName).stem().string();
+    int id;
+    stringstream(idStr) >> id;
+    return id;
+}
+
+shared_ptr<Dic> IndexConstructor::constructIndex()
+{
+    unordered_map<string ,List> hash;
+    for(auto file = files.begin(); file != files.end(); file++)
+    {
+        int fileId = getFileId(*file);
+        cout << "Processing file " << fileId << endl;
+        vector<string> tokens = TokenReader::readAndLowerTokensFromFile(*file);
+        for(auto token = tokens.begin(); token != tokens.end(); token++)
+        {
+            auto list = hash.find(*token); 
+            if(list == hash.end())
+            {
+                List newList(*token);
+                hash.emplace(*token, newList);
+                list = hash.find(*token);
+            }
+            list->second.addPosting(fileId);
+        }
+    }
+    cout << "Sorting terms" << endl;
+    shared_ptr<Dic> dic(new Dic());
+    for(auto itr = hash.begin(); itr != hash.end(); itr++)
+    {
+        dic->addList(itr->first, itr->second);
+    }
+    dic->sortLists();
+    return dic;
+}
+
+IndexConstructor::~IndexConstructor()
+{
+}
diff --git a/simple_ir/IndexConstructor.h b/simple_ir/IndexConstructor.h
new file mode 100644
index 0000000..40d4571
--- /dev/null
+++ b/simple_ir/IndexConstructor.h
@@ -0,0 +1,18 @@
+#pragma once
+#include <string>
+#include <vector>
+#include "Dic.h"
+#include <memory>
+using namespace std;
+
+class IndexConstructor
+{
+private:
+    vector<string> files;
+    int getFileId(string fileName);
+public:
+    IndexConstructor(string folderName, int fileLimit);
+    shared_ptr<Dic> constructIndex();
+    ~IndexConstructor(void);
+};
+
diff --git a/simple_ir/List.cpp b/simple_ir/List.cpp
index 73e3fb3..343c3aa 100644
--- a/simple_ir/List.cpp
+++ b/simple_ir/List.cpp
@@ -24,8 +24,9 @@ int List::getLength()
     return length;
 }
 
-void List::addPosting(string docId)
+void List::addPosting(int docId)
 {
+    // Assume docId are added in increasing order
     // TODO: frequency currently set to 0
     Posting* posting = new Posting(docId, 0);
     if(head == NULL)
@@ -36,9 +37,14 @@ void List::addPosting(string docId)
     }
     else
     {
-        last->next = posting;
-        last = last->next;
-        length ++;
+        // Because docId are added in increasing order we only need to asure
+        // last docId in list doesn't equal to the one we are adding.
+        if(last->getDocId() != docId)
+        {
+            last->next = posting;
+            last = last->next;
+            length ++;
+        }
     }
 }
 
diff --git a/simple_ir/List.h b/simple_ir/List.h
index 2cd554d..e52147e 100644
--- a/simple_ir/List.h
+++ b/simple_ir/List.h
@@ -12,9 +12,9 @@ class List
     Posting* last;
 public:
     List(string term);
-    string getTerm();
+    string getTerm() const;
     int getLength();
-    void addPosting(string docId);
+    void addPosting(int docId);
     Posting* getPostings();
 };
 #endif
diff --git a/simple_ir/Posting.cpp b/simple_ir/Posting.cpp
index e149568..44401ff 100644
--- a/simple_ir/Posting.cpp
+++ b/simple_ir/Posting.cpp
@@ -3,7 +3,7 @@
 #include<string>
 #include"Posting.h"
 using namespace std;
-Posting::Posting(string docId, int fq)
+Posting::Posting(int docId, int fq)
 {
     this->docId = docId;
     this->fq = fq;
@@ -15,7 +15,7 @@ int Posting::freq()
     return fq;
 }
 
-string Posting::getDocId()
+int Posting::getDocId()
 {
     return docId;
 }
\ No newline at end of file
diff --git a/simple_ir/Posting.h b/simple_ir/Posting.h
index bcaf940..8976ddd 100644
--- a/simple_ir/Posting.h
+++ b/simple_ir/Posting.h
@@ -8,12 +8,12 @@ class Posting
 {
 private:
     int fq;//频率
-    string docId;
+    int docId;
 
 public:
-    Posting(string docId, int fq);
+    Posting(int docId, int fq);
     Posting* next;
-    string getDocId();
+    int getDocId();
     int freq();//得到频率
 };
 #endif
diff --git a/simple_ir/main.cpp b/simple_ir/main.cpp
index 79966ab..904375d 100644
--- a/simple_ir/main.cpp
+++ b/simple_ir/main.cpp
@@ -2,15 +2,25 @@
 #include "TokenReader.h"
 #include "Dic.h"
 #include "test.h"
-
+#include "IndexConstructor.h"
 using namespace std;
 
 
 
 int main(int argc, char** argv)
 {
-    testDic();
-
+    //testDic();
+    IndexConstructor constructor("../Reuters", 100);
+    auto dic = constructor.constructIndex();
+    string term("commercial");
+    cout << "Search for term " << term << endl;
+    auto list = dic->getListByTerm(term);
+    Posting* posting = list->getPostings();
+    while(posting != NULL)
+    {
+        cout << posting->getDocId() << endl;
+        posting = posting->next;
+    }
     //TokenReader::readAndLowerTokensFromFile("../Reuters/10.html");
 
     int i;
diff --git a/simple_ir/simple_ir.vcxproj b/simple_ir/simple_ir.vcxproj
index 54a5fa2..242e4c5 100644
--- a/simple_ir/simple_ir.vcxproj
+++ b/simple_ir/simple_ir.vcxproj
@@ -40,7 +40,8 @@
   <PropertyGroup Label="UserMacros" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ReferencePath>$(ReferencePath)</ReferencePath>
-    <IncludePath>E:\boost_1_55_0;$(IncludePath)</IncludePath>
+    <IncludePath>E:\local\boost_1_55_0;$(IncludePath)</IncludePath>
+    <LibraryPath>E:\local\boost_1_55_0\lib32-msvc-11.0;$(LibraryPath)</LibraryPath>
   </PropertyGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
@@ -66,6 +67,7 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClCompile Include="Dic.cpp" />
+    <ClCompile Include="IndexConstructor.cpp" />
     <ClCompile Include="List.cpp" />
     <ClCompile Include="main.cpp" />
     <ClCompile Include="Posting.cpp" />
@@ -74,6 +76,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="Dic.h" />
+    <ClInclude Include="IndexConstructor.h" />
     <ClInclude Include="List.h" />
     <ClInclude Include="Posting.h" />
     <ClInclude Include="test.h" />
diff --git a/simple_ir/test.cpp b/simple_ir/test.cpp
index 8be85a1..3168f03 100644
--- a/simple_ir/test.cpp
+++ b/simple_ir/test.cpp
@@ -2,13 +2,14 @@
 #include "Dic.h"
 #include "test.h"
 
+
 using namespace std;
 
 void testDic()
 {
     Dic* dic = new Dic();
     dic->sortLists();
-    List* list = dic->getListByTerm("a");
+    auto list = dic->getListByTerm("a");
     if(list != NULL)
         cout << "Error!" << endl;
     dic->addList("a");
@@ -43,17 +44,17 @@ void testList()
         cout << "Error!" << endl;
     if(list->getLength() != 0)
         cout << "Error!" << endl;
-    list->addPosting("1");
-    list->addPosting("2");
-    list->addPosting("3");
+    list->addPosting(1);
+    list->addPosting(2);
+    list->addPosting(3);
     Posting *posting = list->getPostings();
-    if(posting->getDocId() != "1")
+    if(posting->getDocId() != 1)
         cout << "Error!" << endl;
     posting = posting->next;
-    if(posting->getDocId() != "2")
+    if(posting->getDocId() != 2)
         cout << "Error!" << endl;
     posting = posting->next;
-    if(posting->getDocId() != "3")
+    if(posting->getDocId() != 3)
         cout << "Error!" << endl;
     posting = posting->next;
     if(posting != NULL)