diff --git a/cs677/pa4/Makefile b/cs677/pa4/Makefile
index 5694c46..1b492ea 100644
--- a/cs677/pa4/Makefile
+++ b/cs677/pa4/Makefile
@@ -1,9 +1,10 @@
 
 CXX := mpiCC
 TARGET := maximum-parsimony
-OBJS := Sequence.o
+OBJS := maximum-parsimony.o
+OBJS += Sequence.o
 OBJS += ElementSet.o
-OBJS += maximum-parsimony.o
+OBJS += PTree.o
 
 all: $(TARGET)
 
diff --git a/cs677/pa4/PTree.cc b/cs677/pa4/PTree.cc
new file mode 100644
index 0000000..bb08cc0
--- /dev/null
+++ b/cs677/pa4/PTree.cc
@@ -0,0 +1,63 @@
+
+#include <vector>
+#include <iostream>
+#include "PTree.h"
+#include "Sequence.h"
+using namespace std;
+
+PTree::PTree(const vector<Sequence *> & leaves)
+{
+    int num_leaves = leaves.size();
+    if (num_leaves & (num_leaves - 1))
+    {
+        cerr << "Ptree::Ptree(): Number of initializing leaves is not a power of 2!!" << endl;
+    }
+    else
+    {
+        vector<Sequence> * my_leaves = new vector<Sequence>(num_leaves);
+        for (int i = 0; i < num_leaves; i++)
+        {
+            (*my_leaves)[i] = *leaves[i];
+        }
+        myLevels.push_back(my_leaves);
+        for (int level_index = 1, level_size = num_leaves / 2;
+             level_size;
+             level_index++, level_size /= 2)
+        {
+            vector<Sequence> * level = new vector<Sequence>(level_size);
+            for (int i = 0; i < level_size; i++)
+            {
+                (*level)[i] =
+                    (*myLevels[level_index-1])[2*i].parent(
+                        (*myLevels[level_index-1])[2*i+1]
+                    );
+            }
+        }
+    }
+}
+
+PTree::~PTree()
+{
+    for (int i = 0, sz = myLevels.size(); i < sz; i++)
+    {
+        delete myLevels[i];
+    }
+}
+
+void PTree::print(ostream & out, int level, int index,
+    string prefix, string subprefix) const
+{
+    out << prefix;
+    out << myLevels[level][0][index];
+    if (level > 0)
+    {
+        print(out, level - 1, index * 2, subprefix + "+-", subprefix + "| ");
+        print(out, level - 1, index * 2 + 1, subprefix + "`-", subprefix + "  ");
+    }
+}
+
+ostream & operator<<(ostream & out, const PTree & p)
+{
+    p.print(out, p.myLevels.size() - 1, 0, "", "");
+    return out;
+}
diff --git a/cs677/pa4/PTree.h b/cs677/pa4/PTree.h
new file mode 100644
index 0000000..1626c59
--- /dev/null
+++ b/cs677/pa4/PTree.h
@@ -0,0 +1,18 @@
+
+#include <vector>
+#include <string>
+#include "Sequence.h"
+
+class PTree
+{
+private:
+    std::vector< std::vector< Sequence > * > myLevels;
+
+public:
+    PTree(const std::vector<Sequence *> & leaves);
+    ~PTree();
+    void print(std::ostream & out, int level, int index,
+        std::string prefix, std::string subprefix) const;
+
+    friend std::ostream & operator<<(std::ostream & out, const PTree & p);
+};