diff --git a/Arrays & Strings/Duplicates checking cpp b/Arrays & Strings/Duplicates checking cpp
new file mode 100644
index 0000000..bce13b2
--- /dev/null
+++ b/Arrays & Strings/Duplicates checking cpp	
@@ -0,0 +1,13 @@
+class Solution {
+public:
+    bool containsDuplicate(vector<int>& nums) {
+        sort(nums.begin(), nums.end());  // O(n log n)
+        for (int i = 1; i < nums.size(); ++i) {
+            if (nums[i] == nums[i - 1]) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+
diff --git a/Hashing/Contains_Duplicate/contains_duplicate.cpp b/Hashing/Contains_Duplicate/contains_duplicate.cpp
new file mode 100644
index 0000000..a418360
--- /dev/null
+++ b/Hashing/Contains_Duplicate/contains_duplicate.cpp
@@ -0,0 +1,12 @@
+class Solution {
+public:
+    bool containsDuplicate(vector<int>& nums) {
+        sort(nums.begin(), nums.end());  // O(n log n)
+        for (int i = 1; i < nums.size(); ++i) {
+            if (nums[i] == nums[i - 1]) {
+                return true;
+            }
+        }
+        return false;
+    }
+};