TheAlgorithms · chrdek · Oct 4, 2023 · Oct 4, 2023 · Oct 4, 2023 · Oct 4, 2023
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+/**
+ *  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 }
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+import { HammingWeight } from '../HammingWeight'
+
+describe.each([
+  { inputVal:Number(117), expectedVal: 5 },
+  { inputVal:parseInt(0x9F9,16), expectedVal: 7 },
+  { inputVal:parseInt(0x889193,16), expectedVal: 10 },
+  { inputVal:10043091, expectedVal: 14},
+  { inputVal:parseInt("1101110",2), expectedVal: 5 },
+  { inputVal:parseInt(1101110,2), expectedVal: 5 }
+])('Resulting code checks from $inputVal', ({inputVal, expectedVal}) => {
+  test(`returns ${expectedVal}`, () => {
+    expect(HammingWeight(inputVal)).toBe(expectedVal)
+  })
+})