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Add Kernighan's Algorithm for Counting Set Bits #1107

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Add Kernighan's Algorithm for Counting Set Bits #1107

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b749625
fixes #1106
smitgabani Sep 23, 2022
a6aebb4
add CountSetBits algorithm
smitgabani Sep 23, 2022
ba6f851
add CountSetBits algorithm
smitgabani Sep 23, 2022
d0ba2a3
add CountSetBits algorithm & test
smitgabani Sep 23, 2022
474cc9a
Merge branch 'TheAlgorithms:master' into master
smitgabani Sep 26, 2022
aa4dd7c
Merge branch 'master' of https://github.com/smitgabani/JavaScript
smitgabani Sep 26, 2022
d90363b
fix
smitgabani Sep 26, 2022
9ec4f5f
fix
smitgabani Sep 26, 2022
fe9555b
fix
smitgabani Sep 27, 2022
c0da047
Merge branch 'TheAlgorithms:master' into master
smitgabani Oct 3, 2022
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22 changes: 22 additions & 0 deletions Bit-Manipulation/CountSetBits.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
'use strict'
// author: Smit Gabani
// https://github.com/smitgabani

/**
* explanation link: https://iq.opengenus.org/brian-kernighan-algorithm/
* Brain Kernighan's Algorithm for Counting Set Bits
* @param: num takes number whose number of set bit is to be found
* @return: the count of set bits in the binary equivalent
* */
function CountSetBits (num) {
let cnt = 0
while (num > 0) {
cnt++
num &= (num - 1)
}
return cnt
}
// console.log(CountSetBits(10))
// expected output: 2

export { CountSetBits }
22 changes: 22 additions & 0 deletions Bit-Manipulation/test/CountSetBits.test.js
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import { CountSetBits } from '../CountSetBits'
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I was more thinking something like:

test("CountSetBits", () => {
    const tests = {
        // binary representation: set bits
        '1001': 2,
        '111': 3,
    }
    for (binary in tests)
         expect(CountSetBits(parseInt(binary, 2))).toBe(tests[binary])
})

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I did not use quoted for keys because of:
image

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I did not intend a reversal to the more verbose form. You can even use a list of lists if you like - all you need is a convenient way to test that a certain input leads to a certain output without copy-pasting. Here's another alternative:

const testCountSetBits = (input, expected_output) => expect(CountSetBits(input)).toBe(expected_output)
test('CountSetBits', () => {
    testCountSetBits(25, 3)
    testCountSetBits(36, 2)
})

etc., or, IMO preferable since it makes the binary representation apparent:

const testCountSetBits = (input_bin_str, expected_output) => expect(CountSetBits(parseInt(input, 2))).toBe(expected_output)
test('CountSetBits', () => {
    testCountSetBits("0", 0)
    testCountSetBits("10", 1)
})

etc.


test('check CountSetBits of 25 is 3', () => {
const res = CountSetBits(25)
expect(res).toBe(3)
})
test('check CountSetBits of 36 is 2', () => {
const res = CountSetBits(36)
expect(res).toBe(2)
})
test('check CountSetBits of 16 is 1', () => {
const res = CountSetBits(16)
expect(res).toBe(1)
})
test('check CountSetBits of 58 is 4', () => {
const res = CountSetBits(58)
expect(res).toBe(4)
})
test('check CountSetBits of 0 is 0', () => {
const res = CountSetBits(0)
expect(res).toBe(0)
})