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

Author: everthis

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

@@ -0,0 +1,16 @@
+/**
+ * @param {number} N
+ * @return {number}
+ */
+const bitwiseComplement = function (N) {
+  if (N === 0) return 1
+  // bitmask has the same length as N and contains only ones 1...1
+  let bitmask = N
+  bitmask |= bitmask >> 1
+  bitmask |= bitmask >> 2
+  bitmask |= bitmask >> 4
+  bitmask |= bitmask >> 8
+  bitmask |= bitmask >> 16
+  // flip all bits
+  return bitmask ^ N
+}