diff --git a/src/test/java/com/ossez/lang/tutorial/tests/LintcodeTest.java b/src/test/java/com/ossez/lang/tutorial/tests/LintcodeTest.java
index 92f8e49b06..78b5fe7ff3 100644
--- a/src/test/java/com/ossez/lang/tutorial/tests/LintcodeTest.java
+++ b/src/test/java/com/ossez/lang/tutorial/tests/LintcodeTest.java
@@ -1,251 +1,316 @@
-package com.ossez.lang.tutorial.tests;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.List;
-import java.util.TreeSet;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-import org.junit.Test;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * 
- * @author YuCheng
- *
- */
-public class LintcodeTest {
-
-	private final static Logger logger = LoggerFactory.getLogger(LintcodeTest.class);
-
-	/**
-	 * 53 https://www.lintcode.com/problem/reverse-words-in-a-string/description
-	 */
-	@Test
-	public void test0053ReverseWords() {
-
-		String s = "  Life  doesn't  always    give     us  the       joys we want.";
-
-		String retStr = "";
-		String[] inStr = s.split(" ");
-
-		for (int i = inStr.length - 1; i >= 0; i--) {
-			String cStr = inStr[i].trim();
-			if (!cStr.isEmpty()) {
-				retStr = retStr + " " + cStr;
-			}
-		}
-		retStr = retStr.trim();
-		System.out.println(retStr);
-		// return retStr;
-	}
-
-	/**
-	 * 56 https://www.lintcode.com/problem/two-sum/description
-	 */
-	@Test
-	public void test0056TwoSum() {
-		int[] numbers = { 2, 7, 11, 15 };
-		int target = 9;
-
-		int[] retArray = new int[2];
-
-		for (int i = 0; i < numbers.length; i++) {
-			int intA = numbers[i];
-			int intB = 0;
-
-			for (int j = 1 + i; j < numbers.length; j++) {
-				intB = numbers[j];
-				// SUM CHECK
-				if (target == intA + intB && i < j) {
-					retArray[0] = i;
-					retArray[1] = j;
-					break;
-				}
-			}
-		}
-
-		System.out.println(Arrays.toString(retArray));
-	}
-
-	/**
-	 * 209 https://www.lintcode.com/problem/first-unique-character-in-a-string
-	 */
-	@Test
-	public void test0209FirstUniqChar() {
-		String str = "ddjdz";
-
-		char retStatus = 0;
-
-		// LOOP CHECK
-		for (int i = 0; i < 30; i++) {
-			char c = str.charAt(0);
-			if (str.indexOf(Character.toString(c)) == str.lastIndexOf(Character.toString(c))) {
-				retStatus = c;
-				break;
-			}
-			str = str.replaceAll(Character.toString(c), "");
-		}
-
-		System.out.println("" + retStatus);
-	}
-
-	/**
-	 * 1480 https://www.lintcode.com/problem/dot-product/description
-	 */
-	@Test
-	public void test0423IsValidParentheses() {
-		String s = "([)]";
-
-		boolean retStatus = false;
-		for (int i = 0; i < 3; i++) {
-			s = s.replace("()", "");
-			s = s.replace("{}", "");
-			s = s.replace("[]", "");
-
-			if (s.length() == 0) {
-				retStatus = true;
-				break;
-			}
-		}
-
-		System.out.println(retStatus);
-
-	}
-
-	/**
-	 * 646 https://www.lintcode.com/problem/first-position-unique-character/description
-	 */
-	@Test
-	public void test0646FirstUniqChar() {
-		String s = "saau";
-
-		int retStatus = -1;
-		boolean breakLoop = false;
-
-		int[] iArray = new int[256];
-
-		// NULL CHECK
-		if (s == null || s.length() == 0) {
-			retStatus = -1;
-		}
-
-		// LOOP CHECK
-		for (char c : s.toCharArray()) {
-			iArray[c]++;
-		}
-		for (int i = 0; i < s.length(); i++) {
-			if (iArray[s.charAt(i)] == 1) {
-				retStatus = i;
-				breakLoop = true;
-				break;
-			}
-		}
-
-		// LOOP BREAK CHECK
-		if (!breakLoop) {
-			retStatus = -1;
-		}
-
-		System.out.println(retStatus);
-	}
-
-	/**
-	 * 767 https://www.lintcode.com/problem/reverse-array/description
-	 */
-	@Test
-	public void test0767ReverseArray() {
-		int[] nums = { 1, 2, 3, 4, 5, 6, 7 };
-
-		for (int i = 0; i < nums.length / 2; i++) {
-			int tmp = nums[i];
-			nums[i] = nums[nums.length - 1 - i];
-			nums[nums.length - 1 - i] = tmp;
-		}
-
-		System.out.println(Arrays.toString(nums));
-
-	}
-
-	/**
-	 * 1480 https://www.lintcode.com/problem/dot-product/description
-	 */
-	@Test
-	public void test1377findSubstring() {
-		String str = "";
-		int k = 5;
-
-		HashSet<String> strSet = new HashSet<String>();
-
-		for (int i = 0; i <= str.length() - k; i++) {
-			String subStr = str.substring(i, i + k);
-
-			String pattern = ".*(.).*\\1.*";
-
-			Pattern r = Pattern.compile(pattern);
-
-			Matcher m = r.matcher(subStr);
-			if (!m.find()) {
-				strSet.add(subStr);
-			}
-
-		}
-
-		System.out.println(strSet.size());
-	}
-
-	/**
-	 * 1480 https://www.lintcode.com/problem/dot-product/description
-	 */
-	@Test
-	public void test1480dotProduct() {
-		int[] A = { 1, 1, -1 };
-		int[] B = { 2147483647, 1, 3 };
-
-		int retStatus = 0;
-
-		// LENGTH CHECK
-		if (A.length == 0 || B.length == 0 || A.length != B.length)
-			retStatus = -1;
-
-		// ADDED
-		if (retStatus != -1) {
-			for (int i = 0; i < A.length; i++) {
-				retStatus = retStatus + A[i] * B[i];
-			}
-		}
-
-		System.out.println(retStatus);
-	}
-
-	/**
-	 * 1480 https://www.lintcode.com/problem/dot-product/description
-	 */
-	@Test
-	public void test0044minSubArray() {
-
-		List<Integer> nums = new ArrayList<Integer>();
-		nums.add(1);
-		nums.add(1);
-
-		int min_ending_here = 0;
-		int retStatus = 0;
-
-		for (int i = 0; i < nums.size(); i++) {
-			if (min_ending_here > 0) {
-				min_ending_here = nums.get(i);
-			} else {
-				min_ending_here += nums.get(i);
-			}
-			retStatus = Math.min(retStatus, min_ending_here);
-		}
-
-		System.out.println(retStatus);
-
-	}
-
-}
+package com.ossez.lang.tutorial.tests;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.TreeSet;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import javax.management.ListenerNotFoundException;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.ossez.lang.tutorial.models.ListNode;
+
+/**
+ * 
+ * @author YuCheng
+ *
+ */
+public class LintcodeTest {
+
+	private final static Logger logger = LoggerFactory.getLogger(LintcodeTest.class);
+
+	/**
+	 * 35 https://www.lintcode.com/problem/reverse-linked-list/description
+	 */
+	@Test
+	public void test0035Reverse() {
+		// INIT LINKED LIST
+		ListNode head = new ListNode(1);
+		head.next = new ListNode(2);
+		head.next.next = new ListNode(3);
+
+		// CHECK BEFORE
+		System.out.println(head.val);
+		System.out.println(head.next.val);
+		System.out.println(head.next.next.val);
+
+		// REVERSE
+		ListNode prev = null;
+		while (head != null) {
+			ListNode temp = head.next;
+			head.next = prev;
+			prev = head;
+			head = temp;
+		}
+
+		// CHECK AFTER
+		System.out.println(prev.val);
+		System.out.println(prev.next.val);
+		System.out.println(prev.next.next.val);
+	}
+
+	/**
+	 * 1480 https://www.lintcode.com/problem/dot-product/description
+	 */
+	@Test
+	public void test0044minSubArray() {
+
+		List<Integer> nums = new ArrayList<Integer>();
+		nums.add(1);
+		nums.add(1);
+
+		int min_ending_here = 0;
+		int retStatus = 0;
+
+		for (int i = 0; i < nums.size(); i++) {
+			if (min_ending_here > 0) {
+				min_ending_here = nums.get(i);
+			} else {
+				min_ending_here += nums.get(i);
+			}
+			retStatus = Math.min(retStatus, min_ending_here);
+		}
+
+		System.out.println(retStatus);
+
+	}
+
+	/**
+	 * 53 https://www.lintcode.com/problem/reverse-words-in-a-string/description
+	 */
+	@Test
+	public void test0053ReverseWords() {
+
+		String s = "  Life  doesn't  always    give     us  the       joys we want.";
+
+		String retStr = "";
+		String[] inStr = s.split(" ");
+
+		for (int i = inStr.length - 1; i >= 0; i--) {
+			String cStr = inStr[i].trim();
+			if (!cStr.isEmpty()) {
+				retStr = retStr + " " + cStr;
+			}
+		}
+		retStr = retStr.trim();
+		System.out.println(retStr);
+		// return retStr;
+	}
+
+	/**
+	 * 56 https://www.lintcode.com/problem/two-sum/description
+	 */
+	@Test
+	public void test0056TwoSum() {
+		int[] numbers = { 2, 7, 11, 15 };
+		int target = 9;
+
+		int[] retArray = new int[2];
+
+		for (int i = 0; i < numbers.length; i++) {
+			int intA = numbers[i];
+			int intB = 0;
+
+			for (int j = 1 + i; j < numbers.length; j++) {
+				intB = numbers[j];
+				// SUM CHECK
+				if (target == intA + intB && i < j) {
+					retArray[0] = i;
+					retArray[1] = j;
+					break;
+				}
+			}
+		}
+
+		System.out.println(Arrays.toString(retArray));
+	}
+
+	/**
+	 * 209 https://www.lintcode.com/problem/first-unique-character-in-a-string
+	 */
+	@Test
+	public void test0209FirstUniqChar() {
+		String str = "ddjdz";
+
+		char retStatus = 0;
+
+		// LOOP CHECK
+		for (int i = 0; i < 30; i++) {
+			char c = str.charAt(0);
+			if (str.indexOf(Character.toString(c)) == str.lastIndexOf(Character.toString(c))) {
+				retStatus = c;
+				break;
+			}
+			str = str.replaceAll(Character.toString(c), "");
+		}
+
+		System.out.println("" + retStatus);
+	}
+
+	/**
+	 * 411
+	 * 
+	 * <p>
+	 * <ul>
+	 * <li>@see
+	 * <a href="https://www.cwiki.us/display/ITCLASSIFICATION/Gray+Code">https://www.cwiki.us/display/ITCLASSIFICATION/Gray+Code</a>
+	 * <li>@see<a href="https://www.lintcode.com/problem/gray-code/description">https://www.lintcode.com/problem/gray-code/description</a>
+	 * </ul>
+	 * </p>
+	 * 
+	 */
+	@Test
+	public void test0411GrayCode() {
+		int n = 2;
+
+		List<Integer> retArray = new ArrayList<>();
+
+		if (n == 0) {
+			retArray.add(0);
+		}
+
+		for (int i = 0; i < (2 << (n - 1)); i++) {
+			int g = i ^ (i / 2);
+			retArray.add(g);
+		}
+
+		System.out.println(retArray);
+	}
+
+	/**
+	 * 1480 https://www.lintcode.com/problem/dot-product/description
+	 */
+	@Test
+	public void test0423IsValidParentheses() {
+		String s = "([)]";
+
+		boolean retStatus = false;
+		for (int i = 0; i < 3; i++) {
+			s = s.replace("()", "");
+			s = s.replace("{}", "");
+			s = s.replace("[]", "");
+
+			if (s.length() == 0) {
+				retStatus = true;
+				break;
+			}
+		}
+
+		System.out.println(retStatus);
+
+	}
+
+	/**
+	 * 646 https://www.lintcode.com/problem/first-position-unique-character/description
+	 */
+	@Test
+	public void test0646FirstUniqChar() {
+		String s = "saau";
+
+		int retStatus = -1;
+		boolean breakLoop = false;
+
+		int[] iArray = new int[256];
+
+		// NULL CHECK
+		if (s == null || s.length() == 0) {
+			retStatus = -1;
+		}
+
+		// LOOP CHECK
+		for (char c : s.toCharArray()) {
+			iArray[c]++;
+		}
+		for (int i = 0; i < s.length(); i++) {
+			if (iArray[s.charAt(i)] == 1) {
+				retStatus = i;
+				breakLoop = true;
+				break;
+			}
+		}
+
+		// LOOP BREAK CHECK
+		if (!breakLoop) {
+			retStatus = -1;
+		}
+
+		System.out.println(retStatus);
+	}
+
+	/**
+	 * 767 https://www.lintcode.com/problem/reverse-array/description
+	 */
+	@Test
+	public void test0767ReverseArray() {
+		int[] nums = { 1, 2, 3, 4, 5, 6, 7 };
+
+		for (int i = 0; i < nums.length / 2; i++) {
+			int tmp = nums[i];
+			nums[i] = nums[nums.length - 1 - i];
+			nums[nums.length - 1 - i] = tmp;
+		}
+
+		System.out.println(Arrays.toString(nums));
+
+	}
+
+	/**
+	 * 1480 https://www.lintcode.com/problem/dot-product/description
+	 */
+	@Test
+	public void test1377findSubstring() {
+		String str = "";
+		int k = 5;
+
+		HashSet<String> strSet = new HashSet<String>();
+
+		for (int i = 0; i <= str.length() - k; i++) {
+			String subStr = str.substring(i, i + k);
+
+			String pattern = ".*(.).*\\1.*";
+
+			Pattern r = Pattern.compile(pattern);
+
+			Matcher m = r.matcher(subStr);
+			if (!m.find()) {
+				strSet.add(subStr);
+			}
+
+		}
+
+		System.out.println(strSet.size());
+	}
+
+	/**
+	 * 1480 https://www.lintcode.com/problem/dot-product/description
+	 */
+	@Test
+	public void test1480dotProduct() {
+		int[] A = { 1, 1, -1 };
+		int[] B = { 2147483647, 1, 3 };
+
+		int retStatus = 0;
+
+		// LENGTH CHECK
+		if (A.length == 0 || B.length == 0 || A.length != B.length)
+			retStatus = -1;
+
+		// ADDED
+		if (retStatus != -1) {
+			for (int i = 0; i < A.length; i++) {
+				retStatus = retStatus + A[i] * B[i];
+			}
+		}
+
+		System.out.println(retStatus);
+	}
+
+}