Create HammingWeight.js

chrdek · web-flow · commit a35ce8d8b188 · 2023-10-09T16:37:43.000+03:00
Changes in name of algorithm.
diff --git a/Bit-Manipulation/HammingWeight.js b/Bit-Manipulation/HammingWeight.js
@@ -0,0 +1,40 @@
+/**
+ *  github author: chrdek
+ *  license: GPL-3.0 or later
+ *
+ *  @param {number} b = integer or, binary representation of it
+ *
+ *  The following code generates the "hamming weight" for a binary sequence
+ *  of 32-bit integer values, producing the relevant integer code for it.
+ *
+ *  Returns the overall of bit count population for values up to 65535, inclusive.
+ *  
+ *  This algorithm utilizes minimum amount of byte space reads and can be very easily
+ *  extended to its 64-bit counterpart.
+ *
+ **/
+
+function HammingWeight(b) {
+  //preallocate total number of bytes to count the bits population from
+  let bytes = new Array(65536);
+
+  //count the bit allocation of the binary sequence by shift in place of the resulting bits
+  //can be used with xor as well.
+  const bitAlloc = (bin) => {
+    let counter = 0;
+    while (bin > 0) {
+      counter += bin & 1;
+      bin >>=1;
+      }
+  return counter;
+  }
+
+  //count all 1-bits from entire bit set
+  for (let k=0; k < 65536; k++)
+  bytes[k] = bitAlloc(k);
+
+ //perform bit shifting for integer values for bit-populated result
+ return bytes[b & 0xFFFF] + bytes[b >> 16];
+}
+
+export { HammingWeight }
