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Add code for checking whether given number is a power of 2 or not #759

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Merged
raklaptudirm merged 3 commits into from
Oct 8, 2021
Merged

Add code for checking whether given number is a power of 2 or not #759

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e978f43
Add code and tests for checking power of 2
Aayushi-Mittal Oct 8, 2021
7ce688b
Updated the code and did the required changes
Aayushi-Mittal Oct 8, 2021
3d8a577
Auto-update DIRECTORY.md
Oct 8, 2021
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28 changes: 28 additions & 0 deletions Bit-Manipulation/IsPowerOfTwo.js
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/*
author: @Aayushi-Mittal

This script will check whether the given
number is a power of two or not.

A number will be a power of two if only one bit is set and rest are unset.
This is true for all the cases except 01 because (2^0 = 1) which is not a power of 2.
For eg: 10 (2^1 = 2), 100 (2^2 = 4), 10000 (2^4 = 16)

Reference Link: https://www.hackerearth.com/practice/notes/round-a-number-to-the-next-power-of-2/

If we will subtract 1 from a number that is a power of 2 we will get it's 1's complement.
And we know that 1's complement is just opp. of that number.
So, (n & (n-1)) will be 0.

For eg: (1000 & (1000-1))
1 0 0 0 // Original Number (8)
0 1 1 1 // After Subtracting 1 (8-1 = 7)
_______
0 0 0 0 // will become 0

*/

export const IsPowerOfTwo = (n) => {
if (n != 0 && (n & (n - 1)) == 0) return true
else return false
}
26 changes: 26 additions & 0 deletions Bit-Manipulation/test/IsPowerOfTwo.test.js
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import {IsPowerOfTwo} from '../IsPowerOfTwo'

test('Check if 0 is a power of 2 or not:', () => {
const res = IsPowerOfTwo(0)
expect(res).toBe(false)
})

test('Check if 0 is a power of 2 or not:', () => {
const res = IsPowerOfTwo(1)
expect(res).toBe(false)
})

test('Check if 4 is a power of 2 or not:', () => {
const res = IsPowerOfTwo(4)
expect(res).toBe(true)
})

test('Check if 1024 is a power of 2 or not:', () => {
const res = IsPowerOfTwo(1024)
expect(res).toBe(true)
})

test('Check if 1025 is a power of 2 or not:', () => {
const res = IsPowerOfTwo(1025)
expect(res).toBe(false)
})
1 change: 1 addition & 0 deletions DIRECTORY.md
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## Bit-Manipulation
* [BinaryCountSetBits](https://github.com/TheAlgorithms/Javascript/blob/master/Bit-Manipulation/BinaryCountSetBits.js)
* [IsPowerOfTwo](https://github.com/TheAlgorithms/Javascript/blob/master/Bit-Manipulation/IsPowerOfTwo.js)
* [SetBit](https://github.com/TheAlgorithms/Javascript/blob/master/Bit-Manipulation/SetBit.js)

## Cache
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