diff --git a/contains-duplicate/yayyz.py b/contains-duplicate/yayyz.py
new file mode 100644
index 000000000..c56bbd270
--- /dev/null
+++ b/contains-duplicate/yayyz.py
@@ -0,0 +1,4 @@
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+
+        return len(nums) != len(set(nums))
diff --git a/house-robber/yayyz.py b/house-robber/yayyz.py
new file mode 100644
index 000000000..2dc384d68
--- /dev/null
+++ b/house-robber/yayyz.py
@@ -0,0 +1,16 @@
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        n = len(nums)
+        
+        if n == 1:
+            return nums[0]
+
+        dp = [0] * n
+        dp[0] = nums[0]
+        dp[1] = max(nums[0], nums[1]) 
+
+        # i 번째를 털지 않은 조건과 i번째를 털은 조건 중 max를 비교
+        for i in range(2, n):
+            dp[i] = max(dp[i-1], dp[i-2] + nums[i])
+
+        return dp[-1]
diff --git a/longest-consecutive-sequence/yayyz.py b/longest-consecutive-sequence/yayyz.py
new file mode 100644
index 000000000..f6589a471
--- /dev/null
+++ b/longest-consecutive-sequence/yayyz.py
@@ -0,0 +1,21 @@
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        if len(nums) == 0: 
+            return 0
+        
+        nums = sorted(set(nums))
+        
+        currLength = 1
+        lastNum = nums[0]
+        result = 1
+        
+        for i in range(1, len(nums)):
+            if nums[i] == lastNum + 1:
+                currLength += 1
+            else:
+                currLength = 1
+            
+            result = max(result, currLength)
+            lastNum = nums[i]
+        
+        return result
diff --git a/product-of-array-except-self/yayyz.py b/product-of-array-except-self/yayyz.py
new file mode 100644
index 000000000..e7baf402e
--- /dev/null
+++ b/product-of-array-except-self/yayyz.py
@@ -0,0 +1,16 @@
+class Solution:
+    # prefix, postfix probelm :(
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        output = [1] * len(nums)
+
+        prefix = 1
+        for i in range(len(nums)):
+            output[i] = prefix
+            prefix *= nums[i]
+
+        postfix = 1
+        for i in range(len(nums) -1, -1, -1):
+            output[i] *= postfix
+            postfix *= nums[i]
+
+        return output
diff --git a/two-sum/yayyz.py b/two-sum/yayyz.py
new file mode 100644
index 000000000..c62b495cc
--- /dev/null
+++ b/two-sum/yayyz.py
@@ -0,0 +1,10 @@
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        hashmap = {}
+        for i, num in enumerate(nums):
+            complement = target - num
+            if complement in hashmap:
+                return [hashmap[complement], i]
+            hashmap[num] = i
+
+