Minor fixes. (trekhleb#91)

* Get Bit: Make more terse

* Power of two: Allowed 1 as a valid power of 2.
Power of two: Removed unnecessary exception throwing.

* Fisher Yates: Made more terse

* Least Common Multiple: Fill undefined value

* Greatest Common Divisor: Fill undefined value.
Greatest Common Divisor: Make more terse.

Author: Bruce-Feldman

src/algorithms/math/bits/README.md

@@ -2,12 +2,7 @@
 
 #### Get Bit
 
-This method shifts `1` over by `bitPosition` bits, creating a 
-value that looks like `00100`. Then we perform `AND` operation
-that clears all bits from the original number except the
-`bitPosition` one. Then we compare the result with zero. If 
-result is zero that would mean that original number has `0` at
-position `bitPosition`.
+This method shifts the relevant bit to the zeroth position.  Then we perform 'AND' operation with one which has bit pattern like '00001'.  This clears all bits from the original number except the relevant one.  If the relevant bit is one, the result is '1', otherwise the result is '0'.
 
 > See `getBit` function for further details.
 

src/algorithms/math/bits/getBit.js

@@ -4,5 +4,5 @@
  * @return {number}
  */
 export default function getBit(number, bitPosition) {
-  return (number & (1 << bitPosition)) === 0 ? 0 : 1;
+  return (number >> bitPosition) & 1;
 }

src/algorithms/math/euclidean-algorithm/__test__/euclieanAlgorithm.test.js

@@ -2,7 +2,7 @@ import euclideanAlgorithm from '../euclideanAlgorithm';
 
 describe('euclideanAlgorithm', () => {
   it('should calculate GCD', () => {
-    expect(euclideanAlgorithm(0, 0)).toBeNull();
+    expect(euclideanAlgorithm(0, 0)).toBe(0);
     expect(euclideanAlgorithm(2, 0)).toBe(2);
     expect(euclideanAlgorithm(0, 2)).toBe(2);
     expect(euclideanAlgorithm(1, 2)).toBe(1);

src/algorithms/math/euclidean-algorithm/euclideanAlgorithm.js

@@ -1,32 +1,11 @@
 /**
  * @param {number} originalA
  * @param {number} originalB
- * @return {number|null}
+ * @return {number}
  */
 export default function euclideanAlgorithm(originalA, originalB) {
   const a = Math.abs(originalA);
   const b = Math.abs(originalB);
 
-  if (a === 0 && b === 0) {
-    return null;
-  }
-
-  if (a === 0 && b !== 0) {
-    return b;
-  }
-
-  if (a !== 0 && b === 0) {
-    return a;
-  }
-
-  // Normally we need to do subtraction (a - b) but to prevent
-  // recursion occurs to often we may shorten subtraction to (a % b).
-  // Since (a % b) is normally means that we've subtracted b from a
-  // many times until the difference became less then a.
-
-  if (a > b) {
-    return euclideanAlgorithm(a % b, b);
-  }
-
-  return euclideanAlgorithm(b % a, a);
+  return (b === 0) ? a : euclideanAlgorithm(b, a % b);
 }

src/algorithms/math/is-power-of-two/__test__/isPowerOfTwo.test.js

@@ -1,17 +1,10 @@
 import isPowerOfTwo from '../isPowerOfTwo';
 
 describe('isPowerOfTwo', () => {
-  it('should throw an exception when trying to apply function to negative number', () => {
-    const isNegativePowerOfTwo = () => {
-      isPowerOfTwo(-1);
-    };
-
-    expect(isNegativePowerOfTwo).toThrowError();
-  });
-
   it('should check if the number is made by multiplying twos', () => {
+    expect(isPowerOfTwo(-1)).toBeFalsy();
     expect(isPowerOfTwo(0)).toBeFalsy();
-    expect(isPowerOfTwo(1)).toBeFalsy();
+    expect(isPowerOfTwo(1)).toBeTruthy();
     expect(isPowerOfTwo(2)).toBeTruthy();
     expect(isPowerOfTwo(3)).toBeFalsy();
     expect(isPowerOfTwo(4)).toBeTruthy();

src/algorithms/math/is-power-of-two/__test__/isPowerOfTwoBitwise.test.js

@@ -1,17 +1,10 @@
 import isPowerOfTwoBitwise from '../isPowerOfTwoBitwise';
 
 describe('isPowerOfTwoBitwise', () => {
-  it('should throw an exception when trying to apply function to negative number', () => {
-    const isNegativePowerOfTwo = () => {
-      isPowerOfTwoBitwise(-1);
-    };
-
-    expect(isNegativePowerOfTwo).toThrowError();
-  });
-
   it('should check if the number is made by multiplying twos', () => {
+    expect(isPowerOfTwoBitwise(-1)).toBeFalsy();
     expect(isPowerOfTwoBitwise(0)).toBeFalsy();
-    expect(isPowerOfTwoBitwise(1)).toBeFalsy();
+    expect(isPowerOfTwoBitwise(1)).toBeTruthy();
     expect(isPowerOfTwoBitwise(2)).toBeTruthy();
     expect(isPowerOfTwoBitwise(3)).toBeFalsy();
     expect(isPowerOfTwoBitwise(4)).toBeTruthy();

src/algorithms/math/is-power-of-two/isPowerOfTwo.js

@@ -3,13 +3,8 @@
  * @return {boolean}
  */
 export default function isPowerOfTwo(number) {
-  // Don't work with negative numbers.
-  if (number < 0) {
-    throw new Error('Please provide positive number');
-  }
-
-  // 0 and 1 are not powers of two.
-  if (number <= 1) {
+  // 1 (2^0) is the smallest power of two.
+  if (number < 1) {
     return false;
   }
 

src/algorithms/math/is-power-of-two/isPowerOfTwoBitwise.js

@@ -3,13 +3,8 @@
  * @return {boolean}
  */
 export default function isPowerOfTwoBitwise(number) {
-  // Don't work with negative numbers.
-  if (number < 0) {
-    throw new Error('Please provide positive number');
-  }
-
-  // 0 and 1 are not powers of two.
-  if (number <= 1) {
+  // 1 (2^0) is the smallest power of two.
+  if (number < 1) {
     return false;
   }
 

src/algorithms/math/least-common-multiple/leastCommonMultiple.js

@@ -7,9 +7,5 @@ import euclideanAlgorithm from '../euclidean-algorithm/euclideanAlgorithm';
  */
 
 export default function leastCommonMultiple(a, b) {
-  if (a === 0 && b === 0) {
-    return 0;
-  }
-
-  return Math.abs(a * b) / euclideanAlgorithm(a, b);
+  return ((a === 0) || (b === 0)) ? 0 : Math.abs(a * b) / euclideanAlgorithm(a, b);
 }

src/algorithms/sets/fisher-yates/fisherYates.js

@@ -6,15 +6,9 @@ export default function fisherYates(originalArray) {
   // Clone array from preventing original array from modification (for testing purpose).
   const array = originalArray.slice(0);
 
-  if (array.length <= 1) {
-    return array;
-  }
-
   for (let i = (array.length - 1); i > 0; i -= 1) {
     const randomIndex = Math.floor(Math.random() * (i + 1));
-    const tmp = array[randomIndex];
-    array[randomIndex] = array[i];
-    array[i] = tmp;
+    [array[i], array[randomIndex]] = [array[randomIndex], array[i]];
   }
 
   return array;