Update 1009-complement-of-base-10-integer.js

Author: everthis

1009-complement-of-base-10-integer.js

@@ -14,3 +14,31 @@ const bitwiseComplement = function (N) {
   // flip all bits
   return bitmask ^ N
 }
+
+// another
+
+/**
+ * @param {number} N
+ * @return {number}
+ */
+const bitwiseComplement = function (N) {
+  let X = 1;
+  while (N > X) X = X * 2 + 1;
+  return N ^ X;
+}
+
+// another
+
+/**
+ * @param {number} N
+ * @return {number}
+ */
+const bitwiseComplement = function (N) {
+  if (N === 0) return 1
+  // l is a length of N in binary representation
+  const l = Math.floor(Math.log(N) / Math.log(2)) + 1
+  // bitmask has the same length as num and contains only ones 1...1
+  const bitmask = (1 << l) - 1
+  // flip all bits
+  return bitmask ^ N
+}