diff --git a/contains-duplicate/hyejj19.ts b/contains-duplicate/hyejj19.ts
new file mode 100644
index 0000000000..af954ec098
--- /dev/null
+++ b/contains-duplicate/hyejj19.ts
@@ -0,0 +1,3 @@
+function containsDuplicate(nums: number[]): boolean {
+  return new Set(nums).size !== nums.length;
+}
diff --git a/two-sum/hyejj19.ts b/two-sum/hyejj19.ts
new file mode 100644
index 0000000000..902bf6288a
--- /dev/null
+++ b/two-sum/hyejj19.ts
@@ -0,0 +1,15 @@
+function twoSum(nums: number[], target: number): number[] {
+  const table = new Map();
+
+  for (let i = 0; i < nums.length; i++) {
+    const complement = target - nums[i];
+
+    if (table.has(complement)) {
+      return [table.get(complement)!, i];
+    }
+
+    table.set(nums[i], i);
+  }
+
+  return [];
+}