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Commit792f490

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Add bit manipulation section.
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‎README.md

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@@ -49,6 +49,7 @@ a set of rules that precisely define a sequence of operations.
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###Algorithms by Topic
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***Math**
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*`B`[Bit Manipulation](src/algorithms/math/bits) - set/get/update/clear bits
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*`B`[Factorial](src/algorithms/math/factorial)
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*`B`[Fibonacci Number](src/algorithms/math/fibonacci)
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*`B`[Primality Test](src/algorithms/math/primality-test) (trial division method)

‎src/algorithms/math/bits/README.md

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#Bit Manipulation
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####Get Bit
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This method shifts`1` over by`bitPosition` bits, creating a
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value that looks like`00100`. Then we perform`AND` operation
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that clears all bits from the original number except the
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`bitPosition` one. Then we compare the result with zero. If
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result is zero that would mean that original number has`0` at
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position`bitPosition`.
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>See`getBit` function for further details.
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####Set Bit
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This method shifts`1` over by`bitPosition` bits, creating a
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value that looks like`00100`. Then we perform`OR` operation
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that sets specific bit into`1` but it does not affect on
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other bits of the number.
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>See`setBit` function for further details.
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####Clear Bit
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This method shifts`1` over by`bitPosition` bits, creating a
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value that looks like`00100`. Than it inverts this mask to get
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the number that looks like`11011`. Then`AND` operation is
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being applied to both the number and the mask. That operation
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unsets the bit.
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>See`clearBit` function for further details.
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####Update Bit
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This method is a combination of "Clear Bit" and "Set Bit" methods.
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>See`updateBit` function for further details.
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importclearBitfrom'../clearBit';
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describe('clearBit',()=>{
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it('should clear bit at specific position',()=>{
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// 1 = 0b0001
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expect(clearBit(1,0)).toBe(0);
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expect(clearBit(1,1)).toBe(1);
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expect(clearBit(1,2)).toBe(1);
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// 10 = 0b1010
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expect(clearBit(10,0)).toBe(10);
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expect(clearBit(10,1)).toBe(8);
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expect(clearBit(10,3)).toBe(2);
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});
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});
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importgetBitfrom'../getBit';
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describe('getBit',()=>{
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it('should get bit at specific position',()=>{
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// 1 = 0b0001
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expect(getBit(1,0)).toBe(1);
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expect(getBit(1,1)).toBe(0);
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// 2 = 0b0010
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expect(getBit(2,0)).toBe(0);
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expect(getBit(2,1)).toBe(1);
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// 3 = 0b0011
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expect(getBit(3,0)).toBe(1);
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expect(getBit(3,1)).toBe(1);
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// 10 = 0b1010
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expect(getBit(10,0)).toBe(0);
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expect(getBit(10,1)).toBe(1);
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expect(getBit(10,2)).toBe(0);
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expect(getBit(10,3)).toBe(1);
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});
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});
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importsetBitfrom'../setBit';
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describe('setBit',()=>{
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it('should set bit at specific position',()=>{
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// 1 = 0b0001
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expect(setBit(1,0)).toBe(1);
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expect(setBit(1,1)).toBe(3);
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expect(setBit(1,2)).toBe(5);
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// 10 = 0b1010
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expect(setBit(10,0)).toBe(11);
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expect(setBit(10,1)).toBe(10);
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expect(setBit(10,2)).toBe(14);
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});
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});
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importupdateBitfrom'../updateBit';
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describe('updateBit',()=>{
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it('should update bit at specific position',()=>{
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// 1 = 0b0001
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expect(updateBit(1,0,1)).toBe(1);
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expect(updateBit(1,0,0)).toBe(0);
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expect(updateBit(1,1,1)).toBe(3);
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expect(updateBit(1,2,1)).toBe(5);
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// 10 = 0b1010
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expect(updateBit(10,0,1)).toBe(11);
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expect(updateBit(10,0,0)).toBe(10);
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expect(updateBit(10,1,1)).toBe(10);
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expect(updateBit(10,1,0)).toBe(8);
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expect(updateBit(10,2,1)).toBe(14);
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expect(updateBit(10,2,0)).toBe(10);
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});
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});

‎src/algorithms/math/bits/clearBit.js

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/**
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*@param {number} number
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*@param {number} bitPosition - zero based.
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*@return {number}
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*/
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exportdefaultfunctionclearBit(number,bitPosition){
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constmask=~(1<<bitPosition);
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returnnumber&mask;
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}

‎src/algorithms/math/bits/getBit.js

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/**
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*@param {number} number
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*@param {number} bitPosition - zero based.
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*@return {number}
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*/
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exportdefaultfunctiongetBit(number,bitPosition){
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return(number&(1<<bitPosition))===0 ?0 :1;
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}

‎src/algorithms/math/bits/setBit.js

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/**
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*@param {number} number
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*@param {number} bitPosition - zero based.
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*@return {number}
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*/
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exportdefaultfunctionsetBit(number,bitPosition){
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returnnumber|(1<<bitPosition);
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}

‎src/algorithms/math/bits/updateBit.js

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/**
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*@param {number} number
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*@param {number} bitPosition - zero based.
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*@param {number} bitValue - 0 or 1.
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*@return {number}
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*/
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exportdefaultfunctionupdateBit(number,bitPosition,bitValue){
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// Normalized bit value.
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constbitValueNormalized=bitValue ?1 :0;
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// Init clear mask.
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constclearMask=~(1<<bitPosition);
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// Cleat bit value and then set it up to required value.
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return(number&clearMask)|(bitValueNormalized<<bitPosition);
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}

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