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Add extra testcases for Fibonacci and improve code (#544)

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* Add extra testcases for Fibonacci and improve code
* Fix typos in Fibonacci.js
This commit is contained in:
rahul1995
2020-12-20 22:24:02 +05:30
committed by GitHub
parent 8dd159f37b
commit 8b1e32eb77
2 changed files with 15 additions and 5 deletions
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15
Maths/Fibonacci.js
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@ -102,14 +102,17 @@ const matrixMultiply = (A, B) => {
return C return C
} }
/**
* Computes A raised to the power n i.e. pow(A, n) where A is a square matrix
* @param {*} A the square matrix
* @param {*} n the exponent
*/
// A is a square matrix // A is a square matrix
const matrixExpo = (A, n) => { const matrixExpo = (A, n) => {
A = copyMatrix(A) A = copyMatrix(A)
if (n === 0) return Identity(A.length) // Identity matrix
if (n === 1) return A
// Just like Binary exponentiation mentioned in ./BinaryExponentiationIterative.js // Just like Binary exponentiation mentioned in ./BinaryExponentiationIterative.js
let result = Identity(A.length) let result = Identity(A.length) // Identity matrix
while (n > 0) { while (n > 0) {
if (n % 2 !== 0) result = matrixMultiply(result, A) if (n % 2 !== 0) result = matrixMultiply(result, A)
n = Math.floor(n / 2) n = Math.floor(n / 2)
@ -127,7 +130,9 @@ const FibonacciMatrixExpo = (n) => {
// | | = | | * | | // | | = | | * | |
// |F(n-1)| |1 0| |F(n-2)| // |F(n-1)| |1 0| |F(n-2)|
// F(n, n-1) = pow(A, n-1) * F(1, 0) // Let's rewrite it as F(n, n-1) = A * F(n-1, n-2)
// or F(n, n-1) = A * A * F(n-2, n-3)
// or F(n, n-1) = pow(A, n-1) * F(1, 0)
if (n === 0) return 0 if (n === 0) return 0
@ -135,7 +140,7 @@ const FibonacciMatrixExpo = (n) => {
[1, 1], [1, 1],
[1, 0] [1, 0]
] ]
const poweredA = matrixExpo(A, n - 1) // A raise to the power n const poweredA = matrixExpo(A, n - 1) // A raised to the power n-1
let F = [ let F = [
[1], [1],
[0] [0]

5
Maths/test/Fibonacci.test.js
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@ -30,6 +30,11 @@ describe('Fibonanci', () => {
}) })
it('should return number for FibonnaciMatrixExpo', () => { it('should return number for FibonnaciMatrixExpo', () => {
expect(FibonacciMatrixExpo(0)).toBe(0)
expect(FibonacciMatrixExpo(1)).toBe(1)
expect(FibonacciMatrixExpo(2)).toBe(1)
expect(FibonacciMatrixExpo(3)).toBe(2)
expect(FibonacciMatrixExpo(4)).toBe(3)
expect(FibonacciMatrixExpo(5)).toBe(5) expect(FibonacciMatrixExpo(5)).toBe(5)
}) })
}) })