diff --git a/contains-duplicate/devyejin.py b/contains-duplicate/devyejin.py
new file mode 100644
index 000000000..32b66eabb
--- /dev/null
+++ b/contains-duplicate/devyejin.py
@@ -0,0 +1,4 @@
+class Solution(object):
+    def containsDuplicate(self, nums):
+        return len(nums) != len(set(nums))
+
diff --git a/house-robber/devyejin.py b/house-robber/devyejin.py
new file mode 100644
index 000000000..ddbfe97a1
--- /dev/null
+++ b/house-robber/devyejin.py
@@ -0,0 +1,17 @@
+class Solution(object):
+    def rob(self, nums):
+        length = len(nums)
+
+        if length <= 2:
+            return max(nums)
+
+        dp = [0] * length
+        dp[0] = nums[0]
+        dp[1] = max(nums[0], nums[1])
+
+        for i in range(2, length):
+            dp[i] = max(dp[i - 1], dp[i - 2] + nums[i])
+
+        return dp[-1]
+
+
diff --git a/longest-consecutive-sequence/devyejin.py b/longest-consecutive-sequence/devyejin.py
new file mode 100644
index 000000000..c56d95035
--- /dev/null
+++ b/longest-consecutive-sequence/devyejin.py
@@ -0,0 +1,19 @@
+class Solution(object):
+    def longestConsecutive(self, nums):
+
+        if not nums:
+            return 0
+
+        num_set = set(nums)
+        max_length = 0
+
+        for num in num_set:
+            if num - 1 not in num_set:
+                length = 1
+                while num + length in num_set:
+                    length += 1
+                max_length = max(max_length, length)
+
+        return max_length
+
+
diff --git a/top-k-frequent-elements/devyejin.py b/top-k-frequent-elements/devyejin.py
new file mode 100644
index 000000000..8a082da5b
--- /dev/null
+++ b/top-k-frequent-elements/devyejin.py
@@ -0,0 +1,9 @@
+from collections import Counter
+import heapq
+
+
+class Solution(object):
+    def topKFrequent(self, nums, k):
+        counter = sorted(Counter(nums).items(), key=lambda item: -item[1])
+        return list(num for num, count in counter[:k])
+
diff --git a/two-sum/devyejin.py b/two-sum/devyejin.py
new file mode 100644
index 000000000..be0dc862d
--- /dev/null
+++ b/two-sum/devyejin.py
@@ -0,0 +1,15 @@
+class Solution(object):
+    def twoSum(self, nums, target):
+
+        nums_tuple = sorted(list(enumerate(nums)), key=lambda x: x[1])
+        left, right = 0, len(nums) - 1
+
+        while left < right:
+            temp_sum = nums_tuple[left][1] + nums_tuple[right][1]
+            if temp_sum == target:
+                return [nums_tuple[left][0], nums_tuple[right][0]]
+            elif temp_sum < target:
+                left += 1
+            else:
+                right -= 1
+