diff --git a/contains-duplicate/0-chan.ts b/contains-duplicate/0-chan.ts
new file mode 100644
index 000000000..e768f9c9e
--- /dev/null
+++ b/contains-duplicate/0-chan.ts
@@ -0,0 +1,8 @@
+/**
+ * time complexity : O(n)
+ * space complexity : O(n)
+ */
+function containsDuplicate(nums: number[]): boolean {
+    const hasDuplicate = new Set(nums).size !== nums.length;
+    return hasDuplicate;
+};
diff --git a/number-of-1-bits/0-chan.ts b/number-of-1-bits/0-chan.ts
new file mode 100644
index 000000000..17b8fdba2
--- /dev/null
+++ b/number-of-1-bits/0-chan.ts
@@ -0,0 +1,10 @@
+/**
+ * time complexity : O(logn)
+ * space complexity : O(logn)
+ */
+function hammingWeight(n: number): number {
+    const MAX_NUM = 2147483648 - 1;
+    
+    const  bitwiseOperated = (n & MAX_NUM).toString(2);
+    return  bitwiseOperated.replaceAll('0', '').length;
+};