Added number of 1 bits and counting bits solution

Author: nhistory

counting-bits/nhistory.js

@@ -0,0 +1,26 @@
+var countBits = function (n) {
+  // Create array which has 0 element length of n
+  const dp = new Array(n + 1).fill(0);
+  let offset = 1;
+
+  for (let i = 1; i <= n; i++) {
+    if (offset * 2 === i) offset = i;
+    dp[i] = 1 + dp[i - offset];
+  }
+  return dp;
+};
+
+/**
+      0 -> 0000 -> dp[0] = 0
+      1 -> 0001 -> dp[1] = 1 + dp[1-1] = 1
+      2 -> 0010 -> dp[2] = 1 + dp[2-2] = 1
+      3 -> 0011 -> dp[3] = 1 + dp[3-2] = 2
+      4 -> 0100 -> dp[4] = 1 + dp[4-4] = 1
+      5 -> 0101 -> dp[5] = 1 + dp[5-4] = 2
+      6 -> 0110 -> dp[6] = 1 + dp[6-4] = 2
+      7 -> 0111 -> dp[7] = 1 + dp[7-4] = 3
+      8 -> 1000 -> dp[8] = 1 + dp[8-8] = 1
+   */
+
+// TC: O(n)
+// SC: O(1)

number-of-1-bits/nhistory.js

@@ -0,0 +1,13 @@
+var hammingWeight = function (n) {
+  let count = 0;
+  while (n) {
+    // Check rightmost bit is equal to 1 by using bitwise AND operator
+    count += n & 1;
+    // Remove rightmost bit from n by using right shift operator
+    n >>= 1;
+  }
+  return count;
+};
+
+// TC: O(1) -> The worst case of 32-integer would be O(32)
+// SC: O(1)