diff --git a/Assignment10/bin/RecursiveExercise.class b/Assignment10/bin/RecursiveExercise.class
index 9dec825..4731608 100644
Binary files a/Assignment10/bin/RecursiveExercise.class and b/Assignment10/bin/RecursiveExercise.class differ
diff --git a/Assignment10/bin/RecursiveExerciseNoExtMethod.class b/Assignment10/bin/RecursiveExerciseNoExtMethod.class
new file mode 100644
index 0000000..cb308ef
Binary files /dev/null and b/Assignment10/bin/RecursiveExerciseNoExtMethod.class differ
diff --git a/Assignment10/src/RecursiveExercise.java b/Assignment10/src/RecursiveExercise.java
index 066eea1..90d1e91 100644
--- a/Assignment10/src/RecursiveExercise.java
+++ b/Assignment10/src/RecursiveExercise.java
@@ -13,29 +13,25 @@ public class RecursiveExercise {
 		int head = MyArrayUtil.head(ht);
 		return MyArrayUtil.addAsFirst(head, l);
 	}
+
 	public static int[] reverse(int[] ht) throws Exception {
 		// fill your code here
-		if(ht == null) return null;
+		if (ht == null)
+			return null;
 		if (ht.length == 1)
 			return ht.clone();
-		int temp = ht[0];
-		ht[0] = ht[ht.length - 1];
-		ht[ht.length - 1] = temp;
-		return recursiveInnerSandwich(reverse(MyArrayUtil.tail(removeLast(ht, new int[ht.length-1], 0))),ht.clone());
+		return append(new int[] { ht[ht.length - 1] },
+				append(reverse(MyArrayUtil.tail(removeLast(ht.clone(), new int[ht.length - 1], 0))), new int[] { ht[0] }));
 	}
-	//This method make an array sandwich excluding the bread (index 0 and index last)
-	public static int[] recursiveInnerSandwich(int[] src,int[] dest) throws Exception{
-		if (src==null)return dest;
-		dest[dest.length-src.length-1] = src[0];
-		recursiveInnerSandwich(MyArrayUtil.tail(src),dest);
-		return dest;
-	}
-	//Remove the last element
-	public static int[] removeLast(int[] ia1,int[] ia2,int i) {
-		ia2[i]=ia1[i];
-		if (i==ia2.length-1)return ia2;
-		return removeLast(ia1,ia2,i+1);
+
+	// Remove the last element
+	public static int[] removeLast(int[] ia1, int[] ia2, int i) {
+		ia2[i] = ia1[i];
+		if (i == ia2.length - 1)
+			return ia2;
+		return removeLast(ia1, ia2, i + 1);
 	}
+
 	public static boolean isIn(int x, int[] a) throws Exception {
 		// fill your code here
 		if (a[0] == x)
@@ -58,12 +54,15 @@ public class RecursiveExercise {
 
 	public static int[] shift(int[] ht, int n) throws Exception {
 		// fill your code here
-		if(ht==null)return null;
-		if(n==0)return ht;
+		if (ht == null)
+			return null;
+		if (n == 0)
+			return ht;
 		int temp = ht[0];
 		ht = reverse(MyArrayUtil.addAsFirst(temp, reverse(MyArrayUtil.tail(ht))));
-		return shift(ht,n-1);
+		return shift(ht, n - 1);
 	}
+
 	public static void main(String[] args) throws Exception {
 		// test append, when appending empty array with {1,2,3}
 		int[] a = null;
diff --git a/Assignment10/src/RecursiveExerciseNoExtMethod.java b/Assignment10/src/RecursiveExerciseNoExtMethod.java
new file mode 100644
index 0000000..ef4ee91
--- /dev/null
+++ b/Assignment10/src/RecursiveExerciseNoExtMethod.java
@@ -0,0 +1,162 @@
+import java.util.Arrays;
+
+public class RecursiveExerciseNoExtMethod {
+
+	// return an array that has all data of ht and n,
+	// just like concatenating ht and n.
+	public static int[] append(int[] ht, int[] n) throws Exception {
+		if (ht == null)
+			return n;
+		if (n == null)
+			return ht;
+		int[] l = append(MyArrayUtil.tail(ht), n);
+		int head = MyArrayUtil.head(ht);
+		return MyArrayUtil.addAsFirst(head, l);
+	}
+	public static int[] reverse(int[] ht) throws Exception {
+		// fill your code here
+		if(ht == null) return null;
+		if (ht.length == 1)
+			return ht.clone();
+		int temp = ht[0];
+		ht[0] = ht[ht.length - 1];
+		ht[ht.length - 1] = temp;
+		return recursiveInnerSandwich(reverse(MyArrayUtil.tail(removeLast(ht, new int[ht.length-1], 0))),ht.clone());
+	}
+	//This method make an array sandwich excluding the bread (index 0 and index last)
+	public static int[] recursiveInnerSandwich(int[] src,int[] dest) throws Exception{
+		if (src==null)return dest;
+		dest[dest.length-src.length-1] = src[0];
+		recursiveInnerSandwich(MyArrayUtil.tail(src),dest);
+		return dest;
+	}
+	//Remove the last element
+	public static int[] removeLast(int[] ia1,int[] ia2,int i) {
+		ia2[i]=ia1[i];
+		if (i==ia2.length-1)return ia2;
+		return removeLast(ia1,ia2,i+1);
+	}
+	public static boolean isIn(int x, int[] a) throws Exception {
+		// fill your code here
+		if (a[0] == x)
+			return true;
+		if (a.length == 1)
+			return false;
+		return isIn(x, MyArrayUtil.tail(a.clone()));
+	}
+
+	public static boolean subArray(int[] a1, int[] a2) throws Exception {
+		// fill your code here
+		if (a1 == null)
+			return true;
+		if (isIn(a1[0], a2))
+			return subArray(MyArrayUtil.tail(a1.clone()), a2);
+		if (a1.length == 1)
+			return true;
+		return false;
+	}
+
+	public static int[] shift(int[] ht, int n) throws Exception {
+		// fill your code here
+		if(ht==null)return null;
+		if(n==0)return ht;
+		int temp = ht[0];
+		ht = reverse(MyArrayUtil.addAsFirst(temp, reverse(MyArrayUtil.tail(ht))));
+		return shift(ht,n-1);
+	}
+	public static void main(String[] args) throws Exception {
+		// test append, when appending empty array with {1,2,3}
+		int[] a = null;
+		int[] b = { 1, 2, 3 };
+		int[] ans1 = append(a, b);
+		System.out.println("Append - Expected: 1, 2, 3.");
+		System.out.print("Get: ");
+		MyArrayUtil.print(ans1);
+		System.out.println("");
+
+		// test append, when appending 2 non-empty arrays.
+		int[] c = { 1, 2, 3 };
+		int[] d = { 4, 5, 6 };
+		ans1 = append(c, d);
+		System.out.println("Append - Expected: 1, 2, 3, 4, 5, 6.");
+		System.out.print("Get: ");
+		MyArrayUtil.print(ans1);
+		System.out.println("");
+
+		// test reverse
+		int[] e = { 1, 2, 3, 4, 5 };
+		ans1 = reverse(e);
+		System.out.println("Reverse - Expected: 5, 4, 3, 2, 1.");
+		System.out.print("Get: ");
+		MyArrayUtil.print(ans1);
+		System.out.println("");
+
+		// test isIn
+		boolean b1 = isIn(3, e);
+		System.out.println("isIn - Expected: true.");
+		System.out.println("Get: " + b1 + ".");
+
+		boolean b2 = isIn(7, e);
+		System.out.println("isIn - Expected: false.");
+		System.out.println("Get: " + b2 + ".");
+
+		// test subArray
+		int[] f = { 1, 3, 5 };
+		int[] g = { 1, 2, 3, 4, 5 };
+		int[] h = { 1, 2, 3, 4, 5 };
+		int[] i = null;
+		int[] j = { 1, 4, 5 };
+
+		b1 = subArray(f, g);
+		System.out.println("subArray - Expected: true.");
+		System.out.println("Get: " + b1 + ".");
+
+		b1 = subArray(g, h);
+		System.out.println("subArray - Expected: true.");
+		System.out.println("Get: " + b1 + ".");
+
+		b1 = subArray(i, h);
+		System.out.println("subArray - Expected: true.");
+		System.out.println("Get: " + b1 + ".");
+
+		b1 = subArray(f, j);
+		System.out.println("subArray - Expected: false.");
+		System.out.println("Get: " + b1 + ".");
+
+		b1 = subArray(h, j);
+		System.out.println("subArray - Expected: false.");
+		System.out.println("Get: " + b1 + ".");
+
+		// test shift
+		int[] k = shift(g, 3);
+		System.out.println("shift - Expected: 4, 5, 1, 2, 3.");
+		System.out.print("Get: ");
+		MyArrayUtil.print(k);
+		System.out.println("");
+
+		k = shift(g, 2);
+		System.out.println("shift - Expected: 3, 4, 5, 1, 2.");
+		System.out.print("Get: ");
+		MyArrayUtil.print(k);
+		System.out.println("");
+
+		k = shift(g, 8);
+		System.out.println("shift - Expected: 4, 5, 1, 2, 3.");
+		System.out.print("Get: ");
+		MyArrayUtil.print(k);
+		System.out.println("");
+
+		k = shift(g, 0);
+		System.out.println("shift - Expected: 1, 2, 3, 4, 5.");
+		System.out.print("Get: ");
+		MyArrayUtil.print(k);
+		System.out.println("");
+
+		k = shift(null, 5);
+		System.out.println("shift - Expected: Array empty");
+		System.out.print("Get: ");
+		MyArrayUtil.print(k);
+		System.out.println("");
+	}
+
+}