diff --git a/contains-duplicate/hellojoyworldz.py b/contains-duplicate/hellojoyworldz.py
new file mode 100644
index 000000000..ad4b5ad48
--- /dev/null
+++ b/contains-duplicate/hellojoyworldz.py
@@ -0,0 +1,13 @@
+# - 문제: https://leetcode.com/problems/contains-duplicate/
+# - 해설: https://www.algodale.com/problems/contains-duplicate/
+
+# 217. Contains Duplicate
+# - Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.
+
+from typing import List
+
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        
+        return len(set(nums)) != len(nums)
+
diff --git a/house-robber/hellojoyworldz.py b/house-robber/hellojoyworldz.py
new file mode 100644
index 000000000..1a84cc81f
--- /dev/null
+++ b/house-robber/hellojoyworldz.py
@@ -0,0 +1,18 @@
+# - 문제: https://leetcode.com/problems/house-robber/
+# - 풀이: https://www.algodale.com/problems/house-robber/
+
+from typing import List
+
+
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        prev1 = 0
+        prev2 = 0
+
+        for num in nums:
+            current = max(prev1, prev2 + num)
+            prev2 = prev1
+            prev1 = current
+
+        return prev1
+
diff --git a/longest-consecutive-sequence/hellojoyworldz.py b/longest-consecutive-sequence/hellojoyworldz.py
new file mode 100644
index 000000000..cf7e8a5f9
--- /dev/null
+++ b/longest-consecutive-sequence/hellojoyworldz.py
@@ -0,0 +1,26 @@
+# - 문제: https://leetcode.com/problems/longest-consecutive-sequence/
+# - 풀이: https://www.algodale.com/problems/longest-consecutive-sequence/
+
+# Current complexity:O(NlogN)
+# Suggested complexity:O(N)
+
+from typing import List
+
+
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+
+        sorted_nums = sorted(set(nums))
+
+        max_sequence = 1
+        current_sequence = 1
+
+        for i in range(1, len(sorted_nums)):
+            if sorted_nums[i] - sorted_nums[i - 1] == 1:
+                current_sequence += 1
+                max_sequence = max(max_sequence, current_sequence)
+            else:
+                current_sequence = 1
+
+        return max(max_sequence, current_sequence)
+
diff --git a/top-k-frequent-elements/hellojoyworldz.py b/top-k-frequent-elements/hellojoyworldz.py
new file mode 100644
index 000000000..4fd0d5cfa
--- /dev/null
+++ b/top-k-frequent-elements/hellojoyworldz.py
@@ -0,0 +1,12 @@
+# - 문제: https://leetcode.com/problems/top-k-frequent-elements/
+# - 풀이: https://www.algodale.com/problems/top-k-frequent-elements/
+
+from collections import Counter
+from typing import List
+
+
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        counter = Counter(nums)
+        return [num for num, count in counter.most_common(k)]
+
diff --git a/two-sum/hellojoyworldz.py b/two-sum/hellojoyworldz.py
new file mode 100644
index 000000000..925ce6214
--- /dev/null
+++ b/two-sum/hellojoyworldz.py
@@ -0,0 +1,17 @@
+# - 문제: https://leetcode.com/problems/two-sum/
+# - 해설: https://www.algodale.com/problems/two-sum/
+
+from typing import List
+
+
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        for first_index, first_num in enumerate(nums):
+            for second_index, second_num in enumerate(nums):
+                if first_index == second_index:
+                    continue
+                if first_num + second_num == target:
+                    return [first_index, second_index]
+
+        return []
+