commit 3961bd29a949f6d384d0dd939b46cf44261fec34
Author: Raphael Roberts <raphael.roberts48@gmail.com>
Date:   Wed Oct 9 23:37:20 2019 -0500

    Added files

diff --git a/CharStack.java b/CharStack.java
new file mode 100644
index 0000000..74a04a9
--- /dev/null
+++ b/CharStack.java
@@ -0,0 +1,67 @@
+// The CharStack class that implements a stack of characters
+// Xiwei Wang
+
+public class CharStack
+{
+    // instance variables
+    private char[] m_array;
+    private int m_index;
+    
+    // constructor
+    public CharStack(int cap)
+    {
+        m_array = new char[cap];
+        m_index = 0;
+    }
+
+    // check whether the stack is empty
+    public boolean isEmpty()
+    {
+        if (m_index == 0)
+            return true;
+        else
+            return false;
+    }
+
+    // return the element at the top of the stack
+    public char top()
+    {
+        if (isEmpty())
+            throw new RuntimeException("top attempted on an empty stack");
+        else
+            return m_array[m_index - 1];
+    }
+            
+    // push a character onto the stack
+    public void push(char c)
+    {
+        m_array[m_index] = c;
+        m_index++;
+    }
+    
+    // remove and return the element at the top of the stack
+    public char pop()
+    { 
+        if (isEmpty())
+            throw new RuntimeException("pop attempted on an empty stack");
+        else
+        {
+            char c = m_array[m_index - 1];
+            m_index--;
+
+            return c;
+        }
+    }
+
+    // return a string representation of the stack
+    @Override
+    public String toString()
+    {
+        String stackContent = "";
+        
+        for (int i = m_index - 1; i >= 0; i--)
+            stackContent += m_array[i];
+        
+        return stackContent;  
+    }
+}
diff --git a/LNode.java b/LNode.java
new file mode 100644
index 0000000..0d0fcce
--- /dev/null
+++ b/LNode.java
@@ -0,0 +1,33 @@
+// The LNode class that represents a node in linked lists
+// Do not make any changes to this file!
+// Xiwei Wang
+
+public class LNode 
+{
+    // instance variables
+    private int m_info;
+    private LNode m_link;
+    
+    // constructor
+    public LNode(int info)
+    {
+        m_info = info;
+        m_link = null;
+    }
+    
+    // member methods
+    public void setLink(LNode link)
+    {
+        m_link = link;
+    }
+    
+    public LNode getLink()
+    {
+        return m_link;
+    }
+    
+    public int getInfo()
+    {
+        return m_info;
+    }   
+}
\ No newline at end of file
diff --git a/RecursiveMethods.java b/RecursiveMethods.java
new file mode 100644
index 0000000..e79c0a5
--- /dev/null
+++ b/RecursiveMethods.java
@@ -0,0 +1,46 @@
+// The RecursiveMethods class that implements several recursive solutions
+// Your name here
+
+public class RecursiveMethods 
+{   
+    // This method calls the sumSquareRec method and returns the sum of the 
+    // squares of the elements in the array.
+    public int sumSquares(int[] A)
+    {
+        // Do not make any changes to this method!
+        return sumSquaresRec(A, 0);
+    }    
+
+    // This method takes an integer array as well as an integer (the starting 
+    // index) and returns the sum of the squares of the elements in the array.
+    public int sumSquaresRec(int[] A, int pos)
+    {
+        // TODO: implement this method
+		
+        return -1; // replace this statement with your own return
+    }   
+
+    // This method takes a character stack and converts all lower case letters
+    // to upper case ones.
+    public void upperStackRec(CharStack s)
+    {
+        // TODO: implement this method            
+    }
+    
+    // This method reads a string and returns the string in the reversed order.
+    public String reverseStringRec(String s)
+    {
+        // TODO: implement this method
+		
+        return "dummy string"; // replace this statement with your own return
+    }
+    
+    // This method takes a reference to the head of a linked list.
+    // It returns the reference to the head of the linked list in the reversed order.
+    public LNode reverseListRec(LNode head)
+    {
+        // TODO: implement this method
+		
+        return new LNode(-1); // replace this statement with your own return
+    }
+}
\ No newline at end of file
diff --git a/TestRecursiveMethods.java b/TestRecursiveMethods.java
new file mode 100644
index 0000000..0b3e180
--- /dev/null
+++ b/TestRecursiveMethods.java
@@ -0,0 +1,452 @@
+// Test driver for the RecursiveMethods class
+// Do not make any changes to this file!
+// Xiwei Wang
+
+import java.util.Arrays;
+
+public class TestRecursiveMethods
+{
+    public static void main(String[] args)
+    {
+        RecursiveMethods myMethods = new RecursiveMethods();
+        
+        int numPassedTests = 0;
+        int numTotalTests = 0;
+        String testResult;
+        
+        // Test 1
+        numTotalTests++;
+        int iReturn = -1;
+        testResult = "[Failed]";
+        String eMsg = "N/A";
+        try
+        {
+            int[] myArray = {10};
+            iReturn = myMethods.sumSquares(myArray);
+            
+            if (iReturn == 100)
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": sumSquares(10) ==> " + testResult + "\n Expected: 100" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: " + iReturn + "\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");
+        
+        // Test 2
+        numTotalTests++;
+        iReturn = -1;
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            int[] myArray = {10, 20, 30, 40, 50, 60};
+            iReturn = myMethods.sumSquares(myArray);
+            
+            if (iReturn == 9100)
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": sumSquares(10, 20, 30, 40, 50, 60) ==> " + testResult + "\n Expected: 9100" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: " + iReturn + "\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");
+
+        // Test 3
+        numTotalTests++;
+        CharStack s = new CharStack(5);
+        String sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            s.push('a');
+            myMethods.upperStackRec(s);
+            sReturn = s.toString();
+            
+            if (sReturn.equals("A"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": upperStackRec(\"a\" (from top to bottom)) ==> " + testResult + "\n Expected: \"A\" (from top to bottom)" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\" (from top to bottom)\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");
+        
+        // Test 4
+        numTotalTests++;
+        s = new CharStack(5);
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            s.push('7');
+            s.push('?');
+            s.push('p');
+            myMethods.upperStackRec(s);
+            sReturn = s.toString();
+            
+            if (sReturn.equals("P?7"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": upperStackRec(\"p?7\" (from top to bottom)) ==> " + testResult + "\n Expected: \"P?7\" (from top to bottom)" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\" (from top to bottom)\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");        
+        
+        // Test 5
+        numTotalTests++;
+        s = new CharStack(5);
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            s.push('4');
+            s.push('K');
+            s.push('3');
+            s.push('s');
+            s.push('c');
+            
+            myMethods.upperStackRec(s);
+            sReturn = s.toString();
+            
+            if (sReturn.equals("CS3K4"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": upperStackRec(\"cs3K4\" (from top to bottom)) ==> " + testResult + "\n Expected: \"CS3K4\" (from top to bottom)" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\" (from top to bottom)\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");
+        
+        // Test 6
+        numTotalTests++;
+        s = new CharStack(9);
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            s.push('Z');
+            s.push('y');
+            s.push('X');
+            s.push('|');
+            s.push('E');
+            s.push('d');
+            s.push('C');
+            s.push('b');
+            s.push('A');
+            
+            myMethods.upperStackRec(s);
+            sReturn = s.toString();
+            
+            if (sReturn.equals("ABCDE|XYZ"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": upperStackRec(\"AbCdE|XyZ\" (from top to bottom)) ==> " + testResult + "\n Expected: \"ABCDE|XYZ\" (from top to bottom)" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\" (from top to bottom)\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");        
+        
+        // Test 7
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            String myString = "";
+            sReturn = myMethods.reverseStringRec(myString);
+            
+            if (sReturn.equals(""))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseStringRec(\"\") ==> " + testResult + "\n Expected: \"\"" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\"\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n"); 
+        
+        // Test 8
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            String myString = "a";
+            sReturn = myMethods.reverseStringRec(myString);
+            
+            if (sReturn.equals("a"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseStringRec(\"a\") ==> " + testResult + "\n Expected: \"a\"" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\"\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");    
+        
+        // Test 9
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            String myString = "abc";
+            sReturn = myMethods.reverseStringRec(myString);
+            
+            if (sReturn.equals("cba"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseStringRec(\"abc\") ==> " + testResult + "\n Expected: \"cba\"" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\"\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");
+        
+        // Test 10
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            String myString = "Hello, Data Structures!";
+            sReturn = myMethods.reverseStringRec(myString);
+            
+            if (sReturn.equals("!serutcurtS ataD ,olleH"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseStringRec(\"Hello, Data Structures!\") ==> " + testResult + "\n Expected: \"!serutcurtS ataD ,olleH\"" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: \"" + sReturn + "\"\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");    
+        
+        // Test 11
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            LNode myNode = null;
+            sReturn = traverseList(myMethods.reverseListRec(myNode));
+            
+            if (sReturn.equals("head->null"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseListRec(null) ==> " + testResult + "\n Expected: head->null" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: " + sReturn + "\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n"); 
+        
+        // Test 12
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            LNode myNode = new LNode(20);
+            sReturn = traverseList(myMethods.reverseListRec(myNode));
+            
+            if (sReturn.equals("head->20->null"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseListRec(20) ==> " + testResult + "\n Expected: head->20->null" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: " + sReturn + "\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");  
+        
+        // Test 13
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            LNode myNode = new LNode(20);
+            LNode myNode1 = new LNode(30);
+            LNode myNode2 = new LNode(40);            
+            myNode.setLink(myNode1);
+            myNode1.setLink(myNode2);
+            sReturn = traverseList(myMethods.reverseListRec(myNode));
+            
+            if (sReturn.equals("head->40->30->20->null"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseListRec(20->30->40) ==> " + testResult + "\n Expected: head->40->30->20->null" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: " + sReturn + "\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n"); 
+        
+        // Test 14
+        numTotalTests++;
+        sReturn = "";
+        testResult = "[Failed]";
+        eMsg = "N/A";
+        try
+        {
+            LNode myNode = new LNode(90);
+            LNode myNode1 = new LNode(80);
+            LNode myNode2 = new LNode(70);
+            LNode myNode3 = new LNode(60); 
+            LNode myNode4 = new LNode(50); 
+            LNode myNode5 = new LNode(40); 
+            myNode.setLink(myNode1);
+            myNode1.setLink(myNode2);
+            myNode2.setLink(myNode3);
+            myNode3.setLink(myNode4);
+            myNode4.setLink(myNode5);
+            sReturn = traverseList(myMethods.reverseListRec(myNode));
+            
+            if (sReturn.equals("head->40->50->60->70->80->90->null"))
+            {
+                numPassedTests++;
+                testResult = "[Passed]";
+            }
+        }
+        catch (RuntimeException e)
+        {
+            eMsg = "RuntimeException - \"" + e.getMessage()  + "\"";
+        }
+        
+        System.out.println("Test " + numTotalTests + ": reverseListRec(90->80->70->60->50->40) ==> " + testResult + "\n Expected: head->40->50->60->70->80->90->null" );
+        if (eMsg.equals("N/A"))
+            System.out.println(" Yours: " + sReturn + "\n");
+        else
+            System.out.println(" Yours: " + eMsg + "\n");  
+
+        System.out.println("Total test cases: " + numTotalTests + "\nCorrect: " + numPassedTests + "\nWrong: " + (numTotalTests - numPassedTests));		
+    }
+    
+    public static String traverseList(LNode head)
+    {
+        String listContent = "head->";
+        LNode current = head;
+        
+        while (current != null)
+        {
+            listContent += current.getInfo() + "->";
+            current = current.getLink();
+        }
+        
+        listContent += "null";
+        
+        return listContent;
+    }
+    
+}