diff --git a/Makefile b/Makefile
index 589b77f..3b3ec6b 100644
--- a/Makefile
+++ b/Makefile
@@ -8,3 +8,6 @@ compile:
 
 link:
 	g++ -o bin/main.out build/*.o
+
+clean:
+	rm build/*.o bin/*.out test/OUTPUT/*.txt
diff --git a/bin/main.out b/bin/main.out
index 5b0e09c..458b47c 100755
Binary files a/bin/main.out and b/bin/main.out differ
diff --git a/include/sorts.h b/include/sorts.h
index 700e750..74d531a 100644
--- a/include/sorts.h
+++ b/include/sorts.h
@@ -24,8 +24,8 @@ public:
     void PrintToFile(std::string outputFilename);
     void InsertionSort(void);
     void MergeSort(void);
-    void __MergeSort__(void);
-    void __Merge__(void);
+    void __MergeSort__(int p, int r);
+    void __Merge__(int p, int q, int r);
     void HeapSort(void);
 };
 
diff --git a/src/sorts.cpp b/src/sorts.cpp
index 899cee4..f4b524e 100644
--- a/src/sorts.cpp
+++ b/src/sorts.cpp
@@ -108,17 +108,50 @@ void Sorter::InsertionSort(void)
 
 void Sorter::MergeSort(void)
 {
-    ;
+    __MergeSort__(0, lineCount - 1);
+    return;
 }
 
-void Sorter::__MergeSort__(void)
+void Sorter::__MergeSort__(int p, int r)
 {
-    ;
+    if (p < r)
+    {
+        int q = (p + r) / 2;
+        __MergeSort__(p, q);
+        __MergeSort__(q+1, r);
+        __Merge__(p, q, r);
+    }
+    return;
 }
 
-void Sorter::__Merge__(void)
+void Sorter::__Merge__(int p, int q, int r)
 {
-    ;
+    int n1 = q - p + 1;
+    int n2 = r - q;
+    // L[i - 1] R[j - 1]
+    std::vector<std::string> leftTmp;
+    std::vector<std::string> rightTmp;
+    for (int i = 0; i < n1; i++)
+        leftTmp.push_back(newWordList[p + i]);
+    for (int i = 0; i < n2; i++)
+        rightTmp.push_back(newWordList[q + i + 1]);
+    leftTmp.push_back("ZZZZZ");
+    rightTmp.push_back("ZZZZZ");
+    int i = 0;
+    int j = 0;
+    for (int k = p; k <= r; k++)
+    {
+        if (leftTmp[i] <= rightTmp[j])
+        {
+            newWordList[k] = leftTmp[i];
+            i++;
+        }
+        else
+        {
+            newWordList[k] = rightTmp[j];
+            j++;
+        }
+    }
 }
 
 void Sorter::HeapSort(void)