Add week 2 solutions: counting-bits

Author: gitsunmin

counting-bits/gitsunmin.ts

@@ -0,0 +1,10 @@
+/**
+ * https://leetcode.com/problems/counting-bits/
+ * time complexity : O(n)
+ * space complexity : O(n)
+ */
+function countBits(n: number): number[] {
+    const arr = new Array(n + 1).fill(0);
+    for (let i = 1; i <= n; i++) arr[i] = arr[i >> 1] + (i & 1);
+    return arr;
+}